Help with 17 R6 suspension geometery guru's

Guys, I need some advice! Ive been having suspension issues with my 2017 R6 current suspension set-up. Stock front forks (set at 5mm under fork cap on the triple), k-tech rear shock spring set for my weight 187pounds (set at 296mm length)

Previously I was on 120/180 Pirelli Sc1 dot tire temp 37psi front hot 21psi rear hot, (rear shock set at 299mm) same fork height. The bike was great, but would wear the tires pretty quickly on the sc1 but thats common. Only once I had an issue with the front tire. I trailbraked to the apex, and cracked the throttle right away. It felt like I lifted the front tire and low sided on a pretty fast turn.

Fast forward to last week! I wasnt able to get ahold of 120/180 sc1. But I needed tires for my race, I did get 120/190 pirelli superbike slicks sc1 front and rear. To run these tires I removed a 3mm rear shim so im at 296mm. I had a race, and during practice the bike felt so amazing with the new rubber, it just threw itself in the turns except for one of the turns. For some odd reason the front end was plowing the front tire as im exiting the apex at wot. In that turn it got to the point to where the front end went to full lock and tire tucked, thanfully I was able to save it. Because of this I lowered the front tire 2psi (35psi hot) On race warm up not so lucky! I was a bit excited, I must have entered a turn and completly lost the front tire. I hit my head so hard I blacked out for 2 hours, so I dont know exactly what happened.

What do you guys think caused my issue? why am I not getting good grip in the front end? Should I lower the forks to raise the front end up higher? Should I lower the rear shock at 3mm more and run 293mm? The guys I compete with are all on top brand forks, I noticed there front forks sit lower in the triples. I know I should be on aftermarket cartridges, but im "on a budget" and frankly im running podium on stock cartridges. Issue I have, is that in my area we dont have a suspension tuner. I would have to drive 8 hours to take it to a suspension shop.

 

heres a pic of where the front forks are at

 

Not only do the other racers have their front ends set higher, they probably also have the forks extended by 10mm. You may be running 10+mm shorter than them. So ya, your front end is probably so short that it's out of range. And you may have the whole bike on the nose with the shock at 296-299.

 

Only reason I raised the forks with the 120/180 was because the bike wouldnt turn on wot in chicanes, I would have to blip the throttle for it to transition.

What do you recommend? You think I should lower the forks 10mm, or go for 6mm? What about the rear leave it at 296mm. I thought about hiring a remote suspension tuner like dave moss

 

Theres no way to give solid advice over the internet on such limit info. Spring rates, preloads, track, riding style, and more are needed to give advice down to the millimeter.

Try it all. Make one change. Keep making that change until things get worse. Put it back to the best setting. Then change something else or try the completely opposite direction.

 

Very true!

But what has me stumped, is because the nose is down on the bike, why would it plow the front tire exiting apex? Wouldnt it do the opposite, and keep it from not wheeling out of turns? I would guess the rear tire would break loose first before the front, because the weight is on the front end

 

Pushing the front on exit or running wide can be a symptom of the front end too low. Some ppl say it's because the front is overloaded. Others say it's because the front tire doesn't track well because it lifts off the ground too easy. Both are probably true at diff times in the corner. More front ride height adds trail and anti-squat. Both can be very helpful for finishing corners.

 

Also, we have no idea what the true front ride height is, because the measurement should be from the bottom of the steering stem (or top of the bottom triple, same thing) to the center of the axle. Don't forget to step on the front wheel to extend the top out spring, if there is one. Do this with the bike supported from the triple tree or jack stand of some kind.

Different cartridges can change this measurement.

I have no idea the capabilities of the stock R6 forks but I imagine it's pretty good. What track and what lap time are you running? Did you adjust front spring rates on the front, or just the rear? Sounds like the rear tire is pushing the bike and it's out of balance.

Sounds like you're going fast enough where you need suspension help. Just ship the forks to @metricdevilmoto or another reputable tuner that actually works with racers.

 

One of the racers pretty fast rider, tells me the fastest hes ever gone was on stock r6 forks.

Thanks Gino! I measured from the top of the lower triple while on a triple stand and pressed my foot and forced the wheel down. I got 520mm if you measure from the top of the bottom lower triple to the center axle. I got 482mm from the bottom of the triple to the center axle. I searched old conversations and guys were recommending 525-530mm. Do you recommend I go 6-7mm lower in the front tubes, do I keep the rear at 296mm or remove a 3mm shim? Again im running the 120/190 pirelli sc1 and its tucking the front end hard. But, the way the bike moved was amazing, it felt planted and fast. Just the front tire didnt grip

 

I’m also trying to adjust my 17+ R6 geometry currently because I just had FKR carts installed into a new set of forks, and I forgot to tell the guy doing my suspension to extend them 10mm like my current forks.

My shock is 296 eye to eye, but I just realized the 3mm oem shim is installed too, so I’m at 299 in the rear. I was running the extended forks 5mm above the top triple all of last year without an issue.

I only did 5 laps with the new non-extended forks this past weekend because of rain. I have them flush with the top triples, which is 5mm shorter in the front than with my extended forks. I’m getting a measure of 527mm from top of bottom triples to center of axle pulling the wheel down. I’m on the Dunlop slicks 180 rear. It felt very twitchy. Too twitchy. It felt like it didn’t want to turn when hard on the brakes, but then was very sensitive mid corner. I’ll be removing the shim for this weekend because that should lower the rear about 6mm and keep the front/rear height ratio about where I was with the extended forks.

Your front is even lower. Assuming your 190 rear is a few mm taller than my 180 Dunlop, I can’t imagine the front that low and the rear that high would work well.

 

Haven't read through the thread responses but when you take away rear shim, you reduce swingarm angle and reduce anti squat. Larger rear tire does little to the swingarm angle.
I would predict you would be more prone to plowing the front end at wot.

 

Ya so basically im 7mm lower in the front end then your bike. The 190 pire and 180 dlop are about the same size give or take 1 or 2mm. I think this is what caused me to crash. Im still debating on removing 3mm more in the rear. Hopefully I will have a trackday this friday and I will see how she acts, I was actually loving the front end down.

 

I ran the forks inset into the top triple when they weren't extended. You have a few more mm of height if you want it. Also should you need even more height, don't forget that preload is just a ride-height adjuster with a few side-effects.

I hate that feeling of a short front end not wanting to turn on the brakes. When you finally do let off the brakes a little, the change from not-turning to turning is sudden and not fun.

I agree that 299 is a bit too tall with the front end at the short end of the range. 296 will prob feel better.

 

That is interesting about preload. My extended forks had 6mm of preload on 1.0 springs. The non-extended forks are at 12mm on .95 springs. If preload is a 1:1 height adjustment, I would think my front would have been about the same height with both forks. But it didn’t feel like that at all. Maybe the lighter spring sagged more? I don’t measure sag. Just trying to figure out why it felt so different if preload is height.

 

You are so close to seeing the full picture.

Preload & ride-height are constant changes. Add 1mm more of either and the position of the fork changes only 1mm under all riding conditions.

Springrate is a linear change. Remove 5% springrate and the fork position is 5% lower all the time. Since different riding conditions use diff amounts of stroke, this amount in millimeters changes. Under hard braking you are using most of the stroke, so you are riding at 5% of ~120mm = ~6mm* lower. At half the stroke, you are riding ~3mm* lower. Etc etc.

Your dynamic fork position at the top of the stroke may be very close to what it was before the fork change. But your dynamic fork position near the bottom of the stroke has changed plenty. The fact that preload and springrate affect fork position differently is what makes them great tools for tuning. For ex, if you add more ride-height now, you'll probably be riding higher at the top of the stroke but at comparable height under hard braking. That'll probably be good for hard braking. But who knows if you'll like the feeling near the top of the stroke.

*The real values are a little less than this because of the air spring

 

This comment is indicative of the whole post and I'm glad I'm not a suspension tuner.

You're trying to achieve precision with vagueness. What exactly is a "pretty fast rider", anyways?

I don't believe someone's lap times are the end all be all, but it does help provide your suspension guy a frame of reference. If the lap record is a 1:30, and you're riding around 1:35, your suspension guy knows that you know which side the gas is on. It's also helpful to provide them some frame of context of how much you're riding the bike, and therefore has a better idea on how much you're likely compressing the forks/shock on exit in order to attain said lap time.

None of your replies provide any solid information other than shock length and tire PSI, assuming your tire gauge is even accurate to begin with.

 

If I’m following you correctly, the shorter trail / twitchy feeling could be caused by greater fork travel due to less spring rate as opposed to the static geometry measured sitting on a front stand or when the front is extended on the throttle. If that’s true, that’s probably why it didn’t feel like it turned any quicker wide open through 11a and 11b at NJMP with the new forks. And I didn’t notice any front end issues on the throttle like the original poster is talking about.

 

Not the whole post. I’m busy trying to thread jack this with numbers. Plus this guy is going to take me out in novice, not you in expert, when he further screws up his settings because he thinks 3mm caused his crash, not his lack of smooth throttle control.

 

Pretty much.

Careful with "the shorter trail / twitchy feeling could be caused by greater fork travel". We don't know that shorter trail has anything to do with this. Saying "lighter springs probably caused this terrible feeling because shorter trail" is way different than "lighter springs probably caused this terrible feeling". The first is prob incorrect - at a minimum it's very hard to confirm. So don't bother too much with the "why". Try to decode the why for every setting change is mentally exhausting and may prevent you from trying new things.

 

Where are you riding that doesnt have a tuner within 8 hours? Just curious. I cant imagine any race org that doesnt have an onsite tuner.