Brammo Owners Forum
Brammo Empulse Discussion => Brammo Empulse Mods => Topic started by: implovator on March 20, 2013, 11:28:03 PM
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Update: I put a much more detailed write-up on my blog. http://www.implovator.com/2013/03/suspension-setup-for-the-new-brammo-empulse-r/ (http://www.implovator.com/2013/03/suspension-setup-for-the-new-brammo-empulse-r/)
I finally got around to measuring my static sag and rider sag tonight. The Empulse R is a bit of a heavy bike, and so I expected the static sag to be a little high. It wasn't too bad in the front at 30 mm for static and 40 mm with the rider. The rear was pretty soft at 28 mm static and 41 mm with the rider. I'm going to double check my measurements this weekend and try to bring the rear rider sag to 35 mm. I want to keep the suspension somewhat compliant for road use since I've been finding myself cranked way over and going through some pretty bumpy corners.
BTW, I came up with an interesting way to measure rear sag without help from a friend. I strapped a telescoping bolt retriever to the swingarm near the axle. Then I strapped a 1x6 board under the subframe directly above. To measure the full extension, I lifted the bike up while it was on the side-stand until the rear wheel came off of the ground and then I extended the bolt retriever and measured it. Then I took a measurement with the bike off of the stand with no rider on it (the difference is static sag). Then I hopped on the bike with gear and lightly leaned against a wall with my elbow. I carefully extended the bolt retriever again and then I hopped off and measured it (the difference from fully extended is rider sag).
Front sag is much easier if you just use a zip tie as the marker and repeat the same three measurements.
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What is about the industry standard on sag for a Motorcycle?
In the MTB world we use %. XC 15-25%, trail 20-30%, and All Mountain 25-35%. Although those are pretty generic settings. I used to worry about mm when base lining a customer, but geometries have gotten so slack, and after talking to a suspension tuning company I have calmed down (my old '98 ProFlex is VERY sensitive to sag). We chatted for a minute and I told him how I had learned some of what I know through the motorcycling community. He shared that from what he knew of sport bikes racing mm tend to make a difference in sag. But things we both figured that small differences get amplified at 180mph, much less 200mph.
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What is about the industry standard on sag for a Motorcycle?
That's an interesting question. I ride bikes (dirt) a lot myself, and I'm stunned at how much information is out there for the MTB crowd. For instance, I've been trying to get some info on the Marzocchi forks on the Empulse. Most googlery turns up product info for their MTB products. Same goes for tutorials and what not. Perhaps this is because MTB suspension is still in its infancy and the equipment out there is highly varied. For instance, I've got bikes with front travel from 90mm all the way to 200+mm. Maybe it's because MTBers are geekier? Regardless, it's tough to find good info for motorcycles.
But back to the original question. I don't actually even know how much travel the Empulse has. So I don't even know what that magical middle third of travel on the front and rear is. Furthermore, I am rarely ever able to find sag recommendations for motorcycles given as percentages. It's almost always just mm figures. Does this mean that street bikes have all settled in on the same amount of travel?
Regardless of my quandary, I'm just sticking with Racetech's FAQ recommendations given here: http://racetech.com/page/id/30#3 (http://racetech.com/page/id/30#3)
I'm going to try and set my sag to 30 mm front and rear. I might end up with too much preload on the rear though, so I might try to get a stiffer spring down the road. I still don't know what to think about the excessive rear static sag (without rider). Racetech recommends 0-5mm (and their terminology is rear free sag). I don't know if this is due to the Empulse girth, rearward weight bias, or possibly light rear spring.
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The magazine articles that I have read have said that a sag of about 25% of the overall stroke of the suspension gets you in the ballpark for a sportbike.
Here is what the owner's manual for my 2012 Zero S has to say about setting the rear shock sag:
Rear Shock Adjustment
Spring Adjustment:
Obtaining the correct rear spring preload is critical for
proper handling. The spring preload must be set to
match the weight of the rider. The spring is preloaded
for an 82 kg (180 lb) rider. This puts the rear tire 1/3
of the way through its vertical travel. Heavier riders
require stiffer spring rates. A good approximation of
your rear spring requirements can be found by
measuring the rear suspension’s sag. This
measurement will quickly determine if your rear
spring is approximately correct for your weight. This
adjustment is a recommended guideline; personal
riding preference may vary from the specifications
given.
• Checking Sag
1. Support your motorcycle on a stand
with the rear wheel off the ground.
2. Measure vertically from the rear axle to
the rear fender. Mark this spot as it will
be used for other measurements.
3. Record this measurement, this will be
measurement M1.
4. Remove the motorcycle from the stand.
5. Wearing your normal riding apparel, sit
on the motorcycle.
6. Have an assistant hold the motorcycle
up, your feet should be on both pegs.
7. Bounce the suspension a couple of times.
8. Have a second assistant take a measurement
using the same locations as in step 2.
9. Record this measurement, this will be measurement M2.
10. Subtract the second measurement (M2) from the first measurement (M1).
Zero recommends 50 mm of sag for their “S” model, which has 140 mm of travel at the front forks and 149 mm of travel at the rear.
(Personally, that sounds too sag much to me.)
There is no sag recommendation for the front forks as their preload can not be adjusted without disassembling the forks and installing a different spring spacer - not an easy task on Fast Ace forks.
I wouldn't be at all surprised if the Ohlins website has detailed instructions for setting sag on a motorcycle, as this information comes with the owner's manual when you purchase one of their shock absorbers.
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Holy smokes! I had no idea that the Empulse R was so under-sprung in the rear. I mean, I suspected it was when I took my initial measurements, but I had no idea that it would make such a difference. I finally got around to taking more accurate measurements and setting my sag today. I took it for a quick test ride and it was phenomenal!
Here's my factory setup. I'm using terms from Racetech where free sag is riderless and static sag is with the rider.
Factory:
Front Free Sag: 26.5mm
Front Static Sag: 38mm
Rear Free Sag: 28.5mm
Rear Static Sag: 51.5mm
Rear Threads Past Collar: 8mm
My goal was to get to the middle of Racetech's street recommendation which would would have been a front static sag of 32.5mm and a rear static sag of 32.5mm. This seemed pretty feasible for the front, but the back was going to have to come in by a lot. This is what I ended up with.
New:
Front Free Sag: 22.5mm
Front Static Sag: 33mm
Front Preload (turns from initial): 3
Rear Free Sag: 19mm
Rear Static Sag: 41.5mm
Rear Preload (threads past collar): 12mm
I ended up stopping way short on the rear end, since I felt uncomfortable adding so much preload. If I don't think it's perfect after doing a few rounds of dampening adjustments, then I might order a new spring for the rear. I think the springs for the front are just fine.
Riding Impressions:
When I first got the Empulse, I thought the back end felt harsh. I mean some of the bumps were bone-jarring. I'm not that heavy at 165 lbs and so I just figured the backend was really stiff. Well no it wasn't. The backend felt harsh because it was so deep in its travel that it was probably bottoming out. After making this adjustment, the big bumps are very distinct, but the rear end now works to suck them up. It feels like a sportbike should. A sportbike is not a touring bike and so it doesn't mask the bumps. It just makes them less catastrophic. I also found the backend to be way smoother over high speed highway bumps. Overall, it's just way more compliant.
My turn-in was affected a little. With the additional preload, it takes more rider input to get the weight bias forward when turning in. So now I just go in hotter and trail brake more.
I'm getting more squat mid-corner once I roll on the throttle and so I have to use my weight to keep the bike leaned over since the front end isn't pulling the bike in. This probably has something to do with the backend being a little soft still. I think I like this though. I feel a lot more of my weight being supported on my upper leg now as I'm pulling the bike down into the corner. In a sense, I'm adding rake to the front end. which is one of the first things that a decent chassis tuner will do in order to gain mid-corner stability and rear grip on exit.
The mid-corner stability is pretty phenomenal now. I have a 270 degree ramp that I take on commute home every day. I took it at about 5 mph faster today...and I haven't even touched the clickers yet. :)
Final Thoughts on the Rear:
I'm trying to figure out why the factory sag was so atypical for a sportbike.
Theory A - It matches the Triumph Street Triple at 50mm rear (according to some guy on Youtube).
Theory B - The Empulse R has a greater-than-normal weight bias to the rear. Anyone know the percentages?
Theory B - Sachs sells their shocks with a standard spring that's appropriate for ICEer like a Ducati Monster but not the somewhat heavy Empulse.
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When I was listening to the webcast from ttxgpp both the riders mentioned that the suspension needed be changed due to the different weight distribution and higher weight. So maybe that's why Brammo set this way out if the box? Maybe we need a different algorithm for electric bikes? Do people shock dyno and weight balance bikes like in cars?
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When I was listening to the webcast from ttxgpp both the riders mentioned that the suspension needed be changed due to the different weight distribution and higher weight. So maybe that's why Brammo set this way out if the box? Maybe we need a different algorithm for electric bikes? Do people shock dyno and weight balance bikes like in cars?
You can usually find information about weight bias on mainstream models. I think that most sportbikes are around 51% front. I was reading a review of the 2013 Street Triple that said they changed the weight bias to 52% front from 49% front. I doubt that any amateur or privateers adjust weight bias at all. The classes with weight restrictions might cause some factory pros to add ballast, but many privateers are probably too broke to lighten their bikes to need ballast in the first place.
I've never had a shock dyno'd, but I'm sure that some suspension shops offer it. Heck, I know of bicycle suspension shops that dyno their stuff. Crazy. I had a really good suspension/chassis shop when I lived in Florida, but he didn't have a dyno. He did have a Computrack system for chassis measuring and setup. It was pretty trick.
Back to your point about weight bias, I wouldn't doubt that the Empulse R is rear-heavy so maybe some extra free/static sag is perfectly acceptable. Like I mentioned earlier, I'll definitely give the stock parts a solid chance and try to get a good setup since I don't like throwing money at my problems. I have a hunch that I will end up getting a new rear spring, but I don't want to order something until I get more information like weight bias, eye-to-eye extended/compressed shock length, and rear-end travel. Hopefully I can get the spring off without a compressor. I'll keep everyone posted. I've been taking pictures too, so maybe I'll do a writeup.
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When I was listening to the webcast from ttxgpp both the riders mentioned that the suspension needed be changed due to the different weight distribution and higher weight. So maybe that's why Brammo set this way out if the box? Maybe we need a different algorithm for electric bikes? Do people shock dyno and weight balance bikes like in cars?
Link? thx
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When I was listening to the webcast from ttxgpp both the riders mentioned that the suspension needed be changed due to the different weight distribution and higher weight. So maybe that's why Brammo set this way out if the box? Maybe we need a different algorithm for electric bikes? Do people shock dyno and weight balance bikes like in cars?
Link? thx
lol it was your webcast!!! Sorry spelled your SN wrong
but I did actually listen to all 3 hours of that!
I think Shelina mentioned the suspension the most and the difference than an ice bike. Am I wrong? Did I miss interpret the convo?
http://brammoforum.com/index.php?topic=1952.0 (http://brammoforum.com/index.php?topic=1952.0)
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Oh! Haha. I was wondering who the heck the TTXGP were putting out a competitor podcast. :D
Hmmm, no I think you are thinking about Eric and I talking about how different the chassis has to be. And what we meant was more the frame and swing arm design and how the forces an electric motor places on the bike are different than an ICE motor does, and hence need to be designed differently. The suspension is an important part of the chassis as I understand it, but in that sense the suspension itself wouldn't be that different. I had heard from one racer that the weight of the elmotos were what was holding the bikes back from fast lap times, and I asked Eric directly, and that's what lead us down the chassis path. Shelina and I did talk about it as well, but as it was conversation from 1-3am I don't recall much of it. :D
BTW, thank you for listening. I'd appreciate a like on facebook or a follow on twitter if you do that sort of thing. You can even sign up for e-mail alerts if you don't do either of those things and have any interest in following my blog and podcast.
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I got a chance to get the Empulse on a shipping scale today .Brammo has given us a balanced 50/50 bike! Solid!
Front: 209.5 lbs.
Rear: 208.5 lbs.
Bias: 50.12% front
So much for one of those theories about the extra rear sag being due to rearward weight balance. This also means that I'll probably end up getting a new spring for the rear. I'm still going to wait until I'm done twiddling knobs.
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418 pounds? Did you already wear 52 pounds off the tires?
Brammo still lists the Empulse at 470 pounds on their website fwiw. But specifications may not hold up in the real world..
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418 pounds? Did you already wear 52 pounds off the tires?
Brammo still lists the Empulse at 470 pounds on their website fwiw. But specifications may not hold up in the real world..
LOL. Actually I think it has more to do with the fact that I didn't have a full tank at 59% SoC. O_o
I'm still mystified by the descrepency. I'm guessing the accuracy of the scale could be off.I do trust the precision, so I figure this is good enough to determine the bias but not the total weight. Maybe someone else can weigh theirs?
My procedure was to place one wheel on the scale and the other wheel on a stack of wood at an equal height. I took the reading and then flipped the bike around.
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418 pounds? Did you already wear 52 pounds off the tires?
Brammo still lists the Empulse at 470 pounds on their website fwiw. But specifications may not hold up in the real world..
We've also been given different motor torque numbers than are listed on the web site and the charge times listed in the provisional manual are different from the spec page. [confused]
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I dialed another 6mm of preload on the rear to bring the static sag to 35mm. Big hit response was greatly improved again. Bad bridge joints at 70 mph were a pleasure. It was absolutely planted in high speed corners. Low speed bump response in corners was sacrificed. That was to be expected, but I'm still going to try and work on it with damping. All in all, I'd say 35mm rear is perfect for aggressive street riding. 40mm might be better for folks more concerned with comfort with still good performance.
Now that I know what 35mm of static sag feels like, I'm going to go ahead and order a new spring since I am likely sacrificing travel. To choose a new spring, I think I'm going to take a bunch of measurements on the shock dimensions and swingarm geometry. Racetech has a couple of forms that you can fill in with your info and then they'll run the numbers and ship you a spring. If I can get my hands on a spring compressor, I'll pull this shock this weekend and get the measurements. I'm post up the numbers.
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...I'd appreciate a like on facebook or a follow on twitter if you do that sort of thing. You can even sign up for e-mail alerts if you don't do either of those things and have any interest in following my blog and podcast.
following you on Twitter! Don't have FB
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implovator,
great info!!!
do you mind taking a picture on where you are adjusting the rear at? Is it the collars to the springs? Are you measuring by turns or distance?
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Yep, you set preload by tightening the collars. It's hard to determine revolutions because you add them so slowly. So I usually measure the threads showing (in mm) past the lock collar.
(http://imageshack.us/a/img266/2421/img0489s.jpg)
The frame blocks direct access to the collars so I use a spanner mounted to a 3/8" socket with a 1" extension. BTW, in this picture, the spanner is set up to loosen a collar, not tighten. DDD
(http://imageshack.us/a/img266/4339/img0486d.jpg)
I found that it's easiest to add preload from the left side of the bike as seen in this next shot. It's a tricky affair, but as long as the spanner is securely in a notch and it is resting straight on the collar, then it doesn't really move. Just make sure you apply your torque in a perfect rotation motion. In this photo, I'm pushing slightly down on the driver. You may have to choke up on the handle and get your fingers under the head of the driver to make sure that you're apply that perfect torque.
(http://imageshack.us/a/img189/623/img0487eb.jpg)
Before making any adjustments, you need to loosen the lock collar. I use screw driver and a rubber mallet. It kind of boogers the notches so I don't recommend using it often. Loosening and tightening the lock collar isn't too bad, but I definitely recommend a spanner for the main collar.
Once the lock collar is loosened, I put a scissor jack under the right side of the frame so as to lift the rear wheel a little. At this point the bike is supported by the jack, the kickstand, and the front wheel. Make sure you have the wheel turned left all of the way into the lock or it might startled you when it flops over while lifting the rear. Lifting the rear takes the load off of the spring so you're only fighting preload at that point when you add more preload. Fighting both can be difficult.
Once you put a few turns on the collar, you're going to want to take it off of the jack and measure the static sag. I use the Racetech method where you measure it fully extended, then you take two measurements without the rider (free sag) and two measurements with the rider (static sag). Really you're shooting for static sag, so checking the free sag supposedly gives you an idea of whether or not you've got the right spring. Maybe an expert in this area can explain that one too me. Anyhow, when you take the two measurements each, you take this first one as the bike settles on the way down. The second measurement is taken when the bike settles on the way back up. So get on it carefully using a natural riding position while you balance against a wall with your elbow for the first measurement. Then while balancing a second time bounce down and let the bike settle on the way up. You take the average of these two readings as a way of compensating for stiction. You subtract that average from the fully extended measurement to get the static sag.
So how do you do this by yourself. Well I use the following setup.
(http://imageshack.us/a/img811/7006/img0467tz.jpg)
That's a wooden dowel bungied under the seat and a telescoping magnetic retriever bungied next to the axle. When I'm balancing on the bike, I reach back carefully and extend the retriever until it hits the dowel and then I get off. Then I measure from the tip of the retriever to the middle of the rear axle.
(http://imageshack.us/a/img20/3441/img0468zr.jpg)
It actually really easy to measure the full extension with the retriever too. You stand on the left side with the bike on the sidestand and pull up on the passenger handle until the rear wheel is off of the ground. Then extend the retriever until it hits the dowel and then push it to the side a tad so that when you put the wheel down it doesn't compress the retriever. Piece of cake.
BTW, checking the front sag is even easier if you use a loose ziptie on the right fork leg. To get the extension, push up on the right bar until the front end lifts, then slide the zip tie up and measure from the bottom of the slider (silver leg) to the top of the zip tie. Now you can do the same for measurements for free sag and static sag using the ziptie in the same way that you used the telescoping retriever.
(http://imageshack.us/a/img826/491/img0466zm.jpg)
To adjust the front preload, just throw a wrench on the red hex head cap on the top of each fork leg. I'm not sure what the starting position is, so I just called it 0 degrees and made sure that I carefully measure and record how many degrees of rotation that I add. I ended up putting three full rotations (tightening) to get 33mm of static sag and I'm about 180 lbs with full gear and a burrito in me.
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...I'd appreciate a like on facebook or a follow on twitter if you do that sort of thing. You can even sign up for e-mail alerts if you don't do either of those things and have any interest in following my blog and podcast.
following you on Twitter! Don't have FB
Thank you! It may seem silly, but it's actually a big help.
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@implovator Dude, that is awesome! Can that be put in the wiki?
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@implovator Dude, that is awesome! Can that be put in the wiki?
Sure thing. It is my intention to type up a full blog post once I finish all of my suspension tinkering. I need to take a few more pictures and write up some better instructions, but once I get the blog up I'd be happy to slap that content on the wiki.
If anyone is thinking of adjusting their own suspension, then I highly recommend jumping right in and setting your sag. It makes a huge difference. I'll be adding a lot of stuff about damping, but quite frankly the difference is not going to be as startling. So far, I think the damping on the Empulse is pretty dang good.
Concerning the the rear sag, if you weight much more than me (180 lbs with gear), then you might have difficulty getting enough preload on the rear to get to a sag number like 35 mm. You should give 40-45 mm a try though and see what you think. If you need a new spring, then hopefully I'll have a tutorial on how to order and replace it yourself. If it requires a spring compressor, then it might hit a tipping point for you where you'll want to ship it off to someone. Heck, after suspending/jacking up your bike and pulling the shock, there's really not much more work to do to get the spring off even if you need a spring compressor. I've got a cheap spring compressor coming on Friday (Amazon Prime FTW), but if it doesn't work out then there's another one that I wanted (non-Prime FTL) that I can probably get for the following weekend.
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Very nice. I can't wait to see the blog post...and the wiki :)
My bike should be here next wednesday...hopefully...I might do this right after the bar end mirrors...
I will probably only go to 45 though at first...i'm about 190 in gear...and not overly aggressive in my riding.
Gavin
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@implovator Dude, that is awesome! Can that be put in the wiki?
I agree!! Thank you so much for the write up!! That helps me a ton! I needed that adapter to get to those collars! Great walk thru!
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I finally finished my write-up on my blog. I took some more shots and included a lot of other little bits...like Hooke's Law. :)
http://www.implovator.com/2013/03/suspension-setup-for-the-new-brammo-empulse-r/ (http://www.implovator.com/2013/03/suspension-setup-for-the-new-brammo-empulse-r/)
Anyhow, it's a bit more verbose than a wiki post should be. When I work up the energy, I'll upload the images to the wiki and try to distill the content down to make it a proper setup. If anyone else wants to jump in, then feel free to steal my photos and text. Maybe just leave a citation? A correctness check would be good too in case my range of settings or initial factory setup was different.
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I just read your complete blog post! Awesome! Super super helpful!
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I just read your complete blog post! Awesome! Super super helpful!
Sure thing. I hope it helps. I definitely poured some time in it. So worth it though. It handles sooooo well now.