Net-Moto :: Community :: Racing :: :: Racing Videos Sponsor :: Contact
 Forums   Features   Trackdays   Moto Crash Incidents   Race Team   CMSP Training   Sponsors      Donate   Terms of Service 
BARF - Bay Area Riders Forum  Home   UserCP   Register   Calendar   Members   FAQ   Search  AMA

Go Back   BARF - Bay Area Riders Forum > Sponsors > The Suspension Forum Presented by GP Suspension


Reply
 
Thread Tools Display Modes
Old 09-20-2017, 11:00 AM   #1
zammer
Tripler
 
zammer's Avatar
 
AMA #3004877
1% Contributor

Join Date: Nov 2013
Location: Albany
Motorcycles: '09 Triumph Street Triple R, '07 GSXR-750 (Track)
Name:
07 GSXR 750 - front end fights me on turn in + hard braking

Ive put ~5 days in on an 07 GSXR 750 I picked up this spring.

Rider: 175 lbs no gear
Front: stock, 1kg/mm springs, but revalved by Superplush supsension for more damping
Rear: Ohlins SU647, 105 spring

Geometry: no fork caps. Front flush with top triple, rear set to 323mm eye to eye. Whole bike has been raised about 5mm this way which was based on JPH and other suspension guru guidance for a setup without caps.

Summary: I rode an 05 R6 ratbike last year and was turning 2:06-2:07's at BW, this year I'm struggling to break 2:10 on this GSXR. I feel the bike struggles to turn in well when I have a lot of brake pressure on turn in or am trail braking too hard. When off the brakes, the bike feels like it carves well and will hold a line just fine.

Jason reduced the preload which helped a bit, it's currently backed out nearly all the way. I'm using almost/all the travel on the front.

Advice? I feel exhausted after a session from wrestling this thing.
zammer is offline   Reply With Quote
Old 09-20-2017, 05:15 PM   #2
afm199
Veteran
 
afm199's Avatar
 
Mod Alumni
Founding Member
Top Percent Poster
Contributor +++++++++ ++++++++++++++3%

Join Date: Sep 2002
Location: Oaklamd
Motorcycles: Yamasuzhonaki 1450
Name: Beelzebub
Raise the rear a couple mm or raise the forks 5 mm.

( That setup is not bad as it is for that bike.). FWIW I run mine around 325 shock and extended caps sticking up about 10 mm, which puts the former top of the fork 3-4 mm below the top of the triple.

It "should" turn fairly easily like that, is the compression damping too stiff? You do absolutely have to get used to turning that bike on the brakes.
__________________
That's not true! The lie is actually the truth! I know. Lots of people know this.
afm199 is online now   Reply With Quote
Old 09-21-2017, 08:43 AM   #3
IL8APEX
Rookie
 
Contributor

Join Date: Nov 2015
Location: San Jose, CA / Royal Oak, MI
Motorcycles: Tiger 800XC
Name: Tom
One Man's Opinion: I think the fork spring rate is a bit high for your weight, unless you're absolutely killing it SuperMoto style trailing in on the brakes.

I'm 220 lbs naked and run the same spring on the same bike with caps, so my forks are probably 10-12mm or so lower in the triples than what you've got up front. Rear length sounds similar, but I would have to measure to confirm. My setup is stable on entry and neutral mid-corner to finish, enabling late brakes and early throttle.

I'm going to guess that your front spring rate is going to put your bike at a good attitude mid-corner but limiting wheel travel and making the tire work harder. Softening the rate MAY increase front grip and help you relax a bit.

-Tom
IL8APEX is offline   Reply With Quote
Old 09-21-2017, 10:15 AM   #4
Not Sure
I like money.
 
Not Sure's Avatar
 
1% Contributor

Join Date: Apr 2004
Location: The Garage
Motorcycles: 07 Weeee,K7 gsxr 750, 97 yzf600r, 05 crf450, 93 cr250, 68 hodaka ace 100
Name: Drew
Quote:
Originally Posted by afm199 View Post
Raise the rear a couple mm or raise the forks 5 mm.

( That setup is not bad as it is for that bike.). FWIW I run mine around 325 shock and extended caps sticking up about 10 mm, which puts the former top of the fork 3-4 mm below the top of the triple.

It "should" turn fairly easily like that, is the compression damping too stiff? You do absolutely have to get used to turning that bike on the brakes.
^This

I am running the same setup... GP fork caps and extended clevis and the bike is phenomenal! I had the same cornering issues before I sourced the parts, fought it for over a season, then installed the caps/shock and instantly made a huge difference.

But, one thing I did that also made the actual 'turn-in' a lot easier was to service the steering damper. A popular 'mod' for the K6/K7 was to up the oil weight in the damper, hopefully helping with head shake... I called the kid who I bought the bike from, and what do you know, he had previously went up to 20wt. I went back to stock weight, and the bike flicks much faster than before... another big improvement when cornering and no more fighting.
Not Sure is offline   Reply With Quote
Old 09-21-2017, 11:07 AM   #5
zammer
Tripler
 
zammer's Avatar
 
AMA #3004877
1% Contributor

Join Date: Nov 2013
Location: Albany
Motorcycles: '09 Triumph Street Triple R, '07 GSXR-750 (Track)
Name:
Quote:
Originally Posted by afm199 View Post
Raise the rear a couple mm or raise the forks 5 mm.

( That setup is not bad as it is for that bike.). FWIW I run mine around 325 shock and extended caps sticking up about 10 mm, which puts the former top of the fork 3-4 mm below the top of the triple.

It "should" turn fairly easily like that, is the compression damping too stiff? You do absolutely have to get used to turning that bike on the brakes.
OK, you mean drop the front of the bike/raise forks in the triples? But it sounds like you and others are running forks that are even lower in the triples than I am (and only another 2mm in the rear)?

We tried lowering the comp damping a bit but it really only helped on downhill turns. It really feels stable when I'm off the brakes on turn in and it exits well, but I find myself missing apexes because I'm wrestling the bike on entry.

Quote:
Originally Posted by IL8APEX View Post
One Man's Opinion: I think the fork spring rate is a bit high for your weight, unless you're absolutely killing it SuperMoto style trailing in on the brakes.

I'm 220 lbs naked and run the same spring on the same bike with caps, so my forks are probably 10-12mm or so lower in the triples than what you've got up front. Rear length sounds similar, but I would have to measure to confirm. My setup is stable on entry and neutral mid-corner to finish, enabling late brakes and early throttle.

I'm going to guess that your front spring rate is going to put your bike at a good attitude mid-corner but limiting wheel travel and making the tire work harder. Softening the rate MAY increase front grip and help you relax a bit.

-Tom
As for spring rate I've always had 0.95 or 0.9's in the front but Jason and others suggested I should stiffen it as I get faster. I'm using all the travel.. but you're right it feels stiff to me.

I'm pretty frustrated with it but I know it can handle well. I'm happy to invest in the caps/extenders if that's what it takes to make the bike right but it sounds to me like the front needs to come down not up more. The Ohlins shock can go quite a bit longer, I think to 328 without any shimming or different clevis.

Also, I'm not currently running a damper until I get the bike sorted out.

Last edited by zammer; 09-21-2017 at 11:11 AM..
zammer is offline   Reply With Quote
Old 09-22-2017, 05:26 AM   #6
IL8APEX
Rookie
 
Contributor

Join Date: Nov 2015
Location: San Jose, CA / Royal Oak, MI
Motorcycles: Tiger 800XC
Name: Tom
Good call on no damper. Get it sorted, don't use the damper as a band aid!

Now that I re-read the post top to bottom I would agree with the trend here: lengthen the shock 1 or 2 mm and re-try.

-Tom
IL8APEX is offline   Reply With Quote
Old 09-22-2017, 10:19 AM   #7
stangmx13
not Stan
 
stangmx13's Avatar
 
Contributor
BrotoGP

Join Date: Feb 2005
Location: San Diego CA
Motorcycles: 04' 600RR, 09' 600RR, 15' R6
Name: Robert
add front ride height

two things make this obvious... the bike turns like shit on the brakes and it turns better off the brakes. off the brakes == higher dynamic ride-height. so, u need to add ride-height to keep the front end higher while using the brakes. u can accomplish this by moving the forks and/or by adding preload. id probably do both.

reducing the fork preload probably didnt help. u said "helped a bit", which makes me think that u imagined the improvement just because someone touched your suspension. you are using all the fork travel because u dont have enough preload on the springs. lets be frank, u arent braking hard yet. if you leave the preload where it is, u will bottom even worse when u gain some confidence on the brakes. so add more preload, probably 4-8 turns.

i agree that your springrate is probably too stiff. .95 or .975 would likely work better. if u had extended fork carts (not caps), id def suggestion .95. but im not so sure otherwise.

sounds like u need to find a new suspension tuner.
__________________
BrotoGP Podcast and on Youtube
WERA #513 / AFM #513R / MotoAmerica #31
Follow me on IG @rwpierce13
Thanks to: RiderzLaw Vortex

Last edited by stangmx13; 09-22-2017 at 10:24 AM..
stangmx13 is online now   Reply With Quote
Old 09-22-2017, 11:08 AM   #8
zammer
Tripler
 
zammer's Avatar
 
AMA #3004877
1% Contributor

Join Date: Nov 2013
Location: Albany
Motorcycles: '09 Triumph Street Triple R, '07 GSXR-750 (Track)
Name:
Quote:
Originally Posted by stangmx13 View Post
add front ride height

two things make this obvious... the bike turns like shit on the brakes and it turns better off the brakes. off the brakes == higher dynamic ride-height. so, u need to add ride-height to keep the front end higher while using the brakes. u can accomplish this by moving the forks and/or by adding preload. id probably do both.

reducing the fork preload probably didnt help. u said "helped a bit", which makes me think that u imagined the improvement just because someone touched your suspension. you are using all the fork travel because u dont have enough preload on the springs. lets be frank, u arent braking hard yet. if you leave the preload where it is, u will bottom even worse when u gain some confidence on the brakes. so add more preload, probably 4-8 turns.

i agree that your springrate is probably too stiff. .95 or .975 would likely work better. if u had extended fork carts (not caps), id def suggestion .95. but im not so sure otherwise.

sounds like u need to find a new suspension tuner.
Thanks Robert, I agree with your analysis. I've been confused that it seems to turn fine off the brakes which seems counterintuitive to me. I don't know if I blame my tuner as I think only after this last weekend at buttonwillow did I play around enough to understand + communicate what I am feeling.

I'm thinking I can run pretty close to Ernie's setup without caps (I can sink the forks 3mm into the top triple without an issue) and extend the shock another 2mm. I'll add some preload and see if that helps.

I'm aware the forks are a little stiff but I figured as I gain some speed I could adjust the preload a bit and make it work. I'm know I'm quite slow (particularly on this bike) and I'm concerned that when I speed up the forks will be bottoming pretty quickly.
zammer is offline   Reply With Quote
Old 09-23-2017, 07:24 AM   #9
afm199
Veteran
 
afm199's Avatar
 
Mod Alumni
Founding Member
Top Percent Poster
Contributor +++++++++ ++++++++++++++3%

Join Date: Sep 2002
Location: Oaklamd
Motorcycles: Yamasuzhonaki 1450
Name: Beelzebub
Quote:
Originally Posted by zammer View Post
OK, you mean drop the front of the bike/raise forks in the triples? But it sounds like you and others are running forks that are even lower in the triples than I am (and only another 2mm in the rear)?

We tried lowering the comp damping a bit but it really only helped on downhill turns. It really feels stable when I'm off the brakes on turn in and it exits well, but I find myself missing apexes because I'm wrestling the bike on entry.



As for spring rate I've always had 0.95 or 0.9's in the front but Jason and others suggested I should stiffen it as I get faster. I'm using all the travel.. but you're right it feels stiff to me.

I'm pretty frustrated with it but I know it can handle well. I'm happy to invest in the caps/extenders if that's what it takes to make the bike right but it sounds to me like the front needs to come down not up more. The Ohlins shock can go quite a bit longer, I think to 328 without any shimming or different clevis.

Also, I'm not currently running a damper until I get the bike sorted out.
Yes, drop the front. I suspect you have too much spring. I weigh 150 and run .95s and will be changing one to a .90 this winter. The extenders really do work, despite the fact that you are raising front and rear with them.

Generally speaking hard turn in on entry is too choppered, and difficulty holding line (push) on exit is too steep.
__________________
That's not true! The lie is actually the truth! I know. Lots of people know this.
afm199 is online now   Reply With Quote
Old 09-23-2017, 09:51 AM   #10
stangmx13
not Stan
 
stangmx13's Avatar
 
Contributor
BrotoGP

Join Date: Feb 2005
Location: San Diego CA
Motorcycles: 04' 600RR, 09' 600RR, 15' R6
Name: Robert
Quote:
Originally Posted by afm199 View Post
Generally speaking hard turn in on entry is too choppered, and difficulty holding line (push) on exit is too steep.
there are so many variables for that generalization on corner entry that i wouldnt try to use it. sure, the bars are easier to turn with less front ride-height. but trail is also a measurement of how effective a bar input is. more trail means the contact patch moves further from the centerline of the bike for a given input. so when the bike is choppered out, u dont need to turn the bars as far to get the bike to lean. on the flip side, w/ a low ride-height and less trail the bars must turn further to get the bike to lean. too low feels useless and too high feels difficult. really, id rather have difficult than useless.

another major variable for all of this is the brakes of course. we cant know where the OP has the dynamic ride-height on corner entry because we dont know how hard hes braking or how early hes trailing off. the control of ride-height is immense. so the brakes absolutely ruin that corner entry generalization.

as for the current situation... stiff springs and a 2:10 pace suggest hes riding high. stock length forks & carts, no preload, and bottoming out suggest that hes riding low. both seem reasonable. however, the lack of preload and bottoming out scream to me that if he reduces the ride-height and brakes harder, hes absolutely SOL
__________________
BrotoGP Podcast and on Youtube
WERA #513 / AFM #513R / MotoAmerica #31
Follow me on IG @rwpierce13
Thanks to: RiderzLaw Vortex
stangmx13 is online now   Reply With Quote
Old 09-24-2017, 06:49 AM   #11
afm199
Veteran
 
afm199's Avatar
 
Mod Alumni
Founding Member
Top Percent Poster
Contributor +++++++++ ++++++++++++++3%

Join Date: Sep 2002
Location: Oaklamd
Motorcycles: Yamasuzhonaki 1450
Name: Beelzebub
What I am curious about is his turn in description. He's having problems turning when trail braking hard. What would make sense to me would be that turn in usually occurs on moderate, not hard braking. It is hard to turn in on hard braking. We use trail braking to help us tailor a turn, but it's a very moderate thing. I don't associate using hard trail braking with helping turn in.
__________________
That's not true! The lie is actually the truth! I know. Lots of people know this.
afm199 is online now   Reply With Quote
Old 09-24-2017, 08:06 AM   #12
stangmx13
not Stan
 
stangmx13's Avatar
 
Contributor
BrotoGP

Join Date: Feb 2005
Location: San Diego CA
Motorcycles: 04' 600RR, 09' 600RR, 15' R6
Name: Robert
Hard braking might not help make it easier to turn in, but that's often the fastest way through a corner. For longer sweeping corners that allow a slow addition of lean angle, I try to hold brake pressure until after I turn in. Noticeable trailing begins after I gain lots of lean angle, not before. The Sweeper at BW is a good example. I'm gonna run some data next year so I can be certain of this.

Of course, without seeing the OP ride, it's hard to know how hard his braking actually is.

Zammer, btw the majority of the laptime around BW has little to do w hard braking. From Cotton Corners all the way past Phil Hill, the focus is roll speed and braking is light. If u don't have enough stability in the entire bike, roll speed would suffer and ud easily add 3 seconds.
__________________
BrotoGP Podcast and on Youtube
WERA #513 / AFM #513R / MotoAmerica #31
Follow me on IG @rwpierce13
Thanks to: RiderzLaw Vortex
stangmx13 is online now   Reply With Quote
Old 09-24-2017, 08:32 AM   #13
zammer
Tripler
 
zammer's Avatar
 
AMA #3004877
1% Contributor

Join Date: Nov 2013
Location: Albany
Motorcycles: '09 Triumph Street Triple R, '07 GSXR-750 (Track)
Name:
I am definitely still a novice but I've felt from Ken Hill podcasts and other pros that I should have moderate brake pressure on at turn in, very roughly between 25-50%.

I think regardless whether you agree with the above or not, the bike fights me pretty hard when I'm on anything more than 10-20%, much more so than my previous bikes. To the point where I'm not dragging knee when I'm trail braking (and often struggling to hit my apex) but easily do when I'm off the brakes altogether.

Does that help?

Quote:
Originally Posted by stangmx13 View Post
Zammer, btw the majority of the laptime around BW has little to do w hard braking. From Cotton Corners all the way past Phil Hill, the focus is roll speed and braking is light. If u don't have enough stability in the entire bike, roll speed would suffer and ud easily add 3 seconds.
Thanks, I appreciate the input. I feel like I'm braking rather hard for the bus stop and phil hill, moreso than I need. But this really became apparent in sunset and when coming into cotton.

Last edited by zammer; 09-24-2017 at 12:42 PM..
zammer is offline   Reply With Quote
Old 09-24-2017, 08:04 PM   #14
afm199
Veteran
 
afm199's Avatar
 
Mod Alumni
Founding Member
Top Percent Poster
Contributor +++++++++ ++++++++++++++3%

Join Date: Sep 2002
Location: Oaklamd
Motorcycles: Yamasuzhonaki 1450
Name: Beelzebub
Quote:
Originally Posted by stangmx13 View Post
Hard braking might not help make it easier to turn in, but that's often the fastest way through a corner. For longer sweeping corners that allow a slow addition of lean angle, I try to hold brake pressure until after I turn in. Noticeable trailing begins after I gain lots of lean angle, not before. The Sweeper at BW is a good example. I'm gonna run some data next year so I can be certain of this.

Of course, without seeing the OP ride, it's hard to know how hard his braking actually is.

Zammer, btw the majority of the laptime around BW has little to do w hard braking. From Cotton Corners all the way past Phil Hill, the focus is roll speed and braking is light. If u don't have enough stability in the entire bike, roll speed would suffer and ud easily add 3 seconds.
Agreed that braking at Bwillow is light and that's kind of my point. The OP is running 2:10s and having a hard time with hard braking turn in... I can't see how that computes and suggest that the hard braking is the problem, not the suspension.
__________________
That's not true! The lie is actually the truth! I know. Lots of people know this.
afm199 is online now   Reply With Quote
Old 09-25-2017, 07:58 AM   #15
stangmx13
not Stan
 
stangmx13's Avatar
 
Contributor
BrotoGP

Join Date: Feb 2005
Location: San Diego CA
Motorcycles: 04' 600RR, 09' 600RR, 15' R6
Name: Robert
Quote:
Originally Posted by afm199 View Post
Agreed that braking at Bwillow is light and that's kind of my point. The OP is running 2:10s and having a hard time with hard braking turn in... I can't see how that computes and suggest that the hard braking is the problem, not the suspension.
i dont understand why ud say this. motos can be setup to turn in adequately on the brakes. most fast riders have their bikes setup like this because theres tons of time to be gained by braking late and holding lots of brake pressure all the way to the apex. i cant imagine a scenario where a rider reports that the bike wont turn in on the brakes and their crew chief says "brake earlier & lighter".

Zammer is likely over-braking for every corner, leading to his lap time. that by itself should make it easier to get to the apex because hes going slower at turn in. its even possible that hes as close or closer to bottom at turn in compared to me. but of course, my bike turns in no matter how hard i brake cuz of its setup.
__________________
BrotoGP Podcast and on Youtube
WERA #513 / AFM #513R / MotoAmerica #31
Follow me on IG @rwpierce13
Thanks to: RiderzLaw Vortex
stangmx13 is online now   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -8. The time now is 06:58 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.