Suspension tuning????

[Mr. Gixxer]

Hey everyone. I don't post here much, i find the search function usually answers my questions. Unfortunately this time it didn't. I'll start with some info. I have an 07 GSXR 1000, lowered 2 inches and stretched 3 inches, every bolt on possible and re-geared. I'm maybe 155lbs ready to ride. My issue is the suspension on this bike. I now with it lowered and stretched it won't handle like a moto gp bike and i don't need it to, i only ride the streets, however i think it should handle better than it does. I've adjusted the geometry so that rake and trail are the same as factory but everything else, compression, rebound, etc all need to be adjusted now. I've tried changing it all myself but i just can't seem to get it to handle decently. I'm also having issues with my rear spinning and sliding around(currently on pilot powers 2ct's) and i'm pretty sure this is suspension related too. I guess the point of this whole post is what do i do now? Are there any suspension tuning shops in Eastern Ma that won't charge an arm and a leg to tune it? Do i need to change out springs because i'm so light? I'm lost.

[SwiftTone]

Shooting in the dark here but by increasing your swingarm length, you effectively increase the leverage effect on the rear suspension. So a stock rear suspension would have been good for your weight(factory suspension is tuned for 150-180lbs rider), now its too undersprung. You're mechanically bottoming out and probabably hydraulically bottoming out too.

You probably have to get a stiffer spring on the rear and possibly revalve too.

Peter and GMD is regarded as a suspension guru, but I'm not sure your bike is within his realms as he deals with sportbikes and track bikes. You can always call and talk to him about it.

[Awesome]

How did you adjust the rake and trail? Custom offset triples? The longer swingarm will act as a bigger lever and the lowering will change the angle that it interacts with the ground. You may hace adjusted to factory rake and trail on the front, which I'm not so sure you did, but the equivalent type of numbers on the back are WAY off factory. There is so much physics involved and you've skewed every base number out into a custom realm. You'll have to pay a suspension guy to get it setup better, but it's never going to ride or handle well other than at the drag strip.

[Mr. Gixxer]

I appreciate the responses guys. Like i said i know it won't handle like a moto gp bike and i'm not riding at a track so i don't need it to however when a lowered, stretched busa pulls away from me in a turn there's an issue. When i lowered the bike i lowered the front first then using adjustable dogbones i lowered the rear making sure the rake was the same as the factory which in turn made the trail correct as well. Since the extended swingarm puts more leverage on the rear shock i assumed i would need to stiffen the rear shock but it is already a pretty jarring ride on bumpy streets.

[Awesome]

I appreciate the responses guys. Like i said i know it won't handle like a moto gp bike and i'm not riding at a track so i don't need it to however when a lowered, stretched busa pulls away from me in a turn there's an issue. When i lowered the bike i lowered the front first then using adjustable dogbones i lowered the rear making sure the rake was the same as the factory which in turn made the trail correct as well. Since the extended swingarm puts more leverage on the rear shock i assumed i would need to stiffen the rear shock but it is already a pretty jarring ride on bumpy streets.

Lowering the same amount front and back does not give you the same rake and trail as factory. Like I said there is more physics involved than you can fathom, rake and trail would be some of the simplest, and it doesn't seem like you've grasped those ones yet. If you want it to handle better, you'll need to go pay a professional, but it still will not handle good.

You should also know that you can't judge performance by how other riders do things better than you.

[Doc]

I appreciate the responses guys. Like i said i know it won't handle like a moto gp bike and i'm not riding at a track so i don't need it to however when a lowered, stretched busa pulls away from me in a turn there's an issue. When i lowered the bike i lowered the front first then using adjustable dogbones i lowered the rear making sure the rake was the same as the factory which in turn made the trail correct as well. Since the extended swingarm puts more leverage on the rear shock i assumed i would need to stiffen the rear shock but it is already a pretty jarring ride on bumpy streets.

If you are not riding at a track why make a trackbike into a cruiser?

[Awesome]

If you are not riding at a track why make a trackbike into a cruiser?

Don't start. People are allowed to do whatever they want with their money and their stuff, regardless of your opinion of what they should do.

[Mr. Gixxer]

For starters it's not a cruiser, it's going to be a drag bike once i buy a second bike for the street. Unfortunately after buying a house the funds are sort of low for a second bike so for now this is my only bike and only option.

Awesome- I measured the rake and trail before and after lowering and they are the same. I used a digital degree finder so unless it happened to break somehow in the 20 minutes it took to lower it then i think it's good in that respect. The only reason i made the busa comment is because i know i can easily out ride him but since lowering the bike finding traction is a huge issue. I've also seen other guys on stretched bikes putting a knee down and flying through corners so i know the suspension can be worked to do it.

[Tunertype]

For starters it's not a cruiser, it's going to be a drag bike once i buy a second bike for the street. Unfortunately after buying a house the funds are sort of low for a second bike so for now this is my only bike and only option.

Awesome- I measured the rake and trail before and after lowering and they are the same. I used a digital degree finder so unless it happened to break somehow in the 20 minutes it took to lower it then i think it's good in that respect. The only reason i made the busa comment is because i know i can easily out ride him but since lowering the bike finding traction is a huge issue. I've also seen other guys on stretched bikes putting a knee down and flying through corners so i know the suspension can be worked to do it.

You could try a basic suspension tuning. try setting your sag for starters at 25-30mm front and rear. If you can't get the sag down to 30mm you need stiffer springs.

Then set your rebound. bounce the bike and it should come up quickly and evenly. If it comes up slow you have too much rebound. if comes up fast and then bounces back down again you need more rebound and compression. If it's uneven you need more or less front to back.

Put a zip tie on the front forks and drive around and brake as hard as you would want to. It should drop down about 1" if it's more then add a little compression. If it barely moves drop some compression out again. do the bounce test watching the down stroke. If it doesn't go down evenly adjust the rear up or down to match the front settings you just set with the zip tie.

After you have basic settings drive it around some more. If you notice a particular problem there are trouble shooting guides out there that will tell you what settings to play with if experience a specific problem. Change the settings one click at a time from the initial settings set as above. If it gets worse go back. Your bike with the longer wheel base and lower center or gravity will need to lean more in a turn to get the same turning radius. So if you were leaning at say 30* in a turn at 75mph before you may need to be leaning at 34* now and since your lower you'll be more likely to scrape things as well like pegs exhaust or your outstretched knee. So a longer wheel base should make getting your knee down easier(lower speeds), but still hurts your turning radius.

A stock or even stretched 'busa should handle better than a stretched AND lowered GSXR. Also corner exit should be faster on a 'busa because it has more torque and power, a stock GSXR should be able to enter the corner faster and have an overall higher cornering speed. Your really not pushing your bike unless your scraping things though. Also tire pressure either too high or too low could be a huge contributor to sliding around as could suspension settings and poor shifting or throttle control.

[maxim_X]

Drag race suspension settings are totally different that a road race setup. If your trying to drag you knee on the bike you drag race on you will see less than favorable results. Anyway you judging your suspension is bad by your lack of ability to drag knee or keep up with 'busas is not a good way to diagnose the issue.

[Tunertype]

Drag race suspension settings are totally different that a road race setup. If your trying to drag you knee on the bike you drag race on you will see less than favorable results. Anyway you judging your suspension is bad by your lack of ability to drag knee or keep up with 'busas is not a good way to diagnose the issue.

Yeah. You will want softer rear so you can squat and load the suspension and get a tiny bit more movement to reduce wheel spin. Also you want more rake to increase stability.

[tsorfas]

No you don't want a softer rear on a drag bike at all

[Mr. Gixxer]

Tunertype, thank you for the info. That's basically what i've found everywhere else and what i've already tried with little luck.

Just so everyone is clear, i know drag and road race settings are different and i understand that i'll have to change it again when i EVENTUALLY hit the strip. Right NOW i'm trying to figure out how to make it handle better on the street WITHOUT going back to stock. I didn't think a 3 inch stretch and lowering it would make it impossible to hit an off ramp at 50mph.

[Tunertype]

No you don't want a softer rear on a drag bike at all

They make special valves so you can loosen up the compression beyond what stock valving will allow just so you can make your shocks softer for drag racing. A harsher rear just makes you wheelie. Longer swing arm and soft suspension are there to help aid weight transfer and reduce wheelies.

Tunertype, thank you for the info. That's basically what i've found everywhere else and what i've already tried with little luck.

You asked about setting it up for your weight. If you already set sag correctly you should know if it's got the right springs/pre-load for your weight.

[Awesome]

Tunertype, thank you for the info. That's basically what i've found everywhere else and what i've already tried with little luck.

Just so everyone is clear, i know drag and road race settings are different and i understand that i'll have to change it again when i EVENTUALLY hit the strip. Right NOW i'm trying to figure out how to make it handle better on the street WITHOUT going back to stock. I didn't think a 3 inch stretch and lowering it would make it impossible to hit an off ramp at 50mph.

Did you torque the shock in to the right spec. That will bind it up for sure. One of the only parts on a bike other than engine internals that I actually use a torque wrench for.

If it's that much of a problem it's likely not the suspension. Check the rest of the bike over. Alignment of rear tire, forks, all the chasis basics. Suspension settings, especially tweeks to damping and preload and all that jazz will not be night and day on major problems.

[Doc]

Don't start. People are allowed to do whatever they want with their money and their stuff, regardless of your opinion of what they should do.

I am just curious... He wants handling in corners but keeps stating "Like i said i know it won't handle like a moto gp bike and i'm not riding at a track so i don't need it to"

You are making my same point, just in a different way.

Lower and stretch away but don't expect it to corner well at all.

As for advice, How old are your tires? Are they flat spotted?

[Mr. Gixxer]

I am just curious... He wants handling in corners but keeps stating "Like i said i know it won't handle like a moto gp bike and i'm not riding at a track so i don't need it to"

You are making my same point, just in a different way.

Lower and stretch away but don't expect it to corner well at all.

As for advice, How old are your tires? Are they flat spotted?

You're missing the part where i've personally seen lowered and stretched bikes corner very well. Yet again i say, i know it can be done.
The front tire is another reason why i'm going over all the suspension. It's starting to get some slight scalloping. I know from many years of working on cars that scalloping is caused because of a suspension issue.

[Awesome]

You're missing the part where i've personally seen lowered and stretched bikes corner very well. Yet again i say, i know it can be done.
The front tire is another reason why i'm going over all the suspension. It's starting to get some slight scalloping. I know from many years of working on cars that scalloping is caused because of a suspension issue.

Scalloping is also, and more often caused by incorrect tire pressure on motorcycles.

[Mr. Gixxer]

Scalloping is also, and more often caused by incorrect tire pressure on motorcycles.

I've ruled out tire pressure because i check it before every ride. Unless the factory tire pressure has to be changed as well since it's lowered and stretched.

[Awesome]

It appears you know everything, you should have no problem fixing it.

[WinVT]

I think I can help you with your handling problem. Raise it and shorten it. Problem solved.

[jasnmar]

I've ruled out tire pressure because i check it before every ride. Unless the factory tire pressure has to be changed as well since it's lowered and stretched.

I think what others have been largely saying is that once you change the geometry of the bike, then the geometry of the bike has been changed. Looking for some "factory" numbers, while other numbers are not factory isn't going to work.

While I understand that your bike isn't keeping up with some others in the curves, that really has nothing to do with anything even if they have been lowered and lengthened.

Lengthening the bike will cause you to have to provide more lean angle to achieve a desired turn radius.
Lowering the bike will prevent you from achieving high lean angles.

Tuning details like compression, preload and damping, while possibly marginally helpful won't get your geometry right.

As was said in the first reply from SwiftTone. Peter @ GMD Computrack knows more about suspension than I'll likely ever know. If you want expertise, take it to him.

[Doc]

You're missing the part where i've personally seen lowered and stretched bikes corner very well. Yet again i say, i know it can be done.
The front tire is another reason why i'm going over all the suspension. It's starting to get some slight scalloping. I know from many years of working on cars that scalloping is caused because of a suspension issue.

Same bike as yours or different?

[timmyho414]

If I knew how to mulit quote i would but since I don't...

You CAN NOT judge your set up based on someone else riding a different bike. -Awesome

sliding the fork tubes up will reduce trail, nothing you do the the rear will get it all back. You can only get it back with triple clamps like Awesome asked about.
call GMD

I would bet with the added leverage of the swing arm the spring needs to be stiffer. You are probable bottoming out as SwiftTone said. IF you put a stiffer spring on to stop that, that spring would overpower the rebound damping of the stock shock. now you need a custom valved shock.
call GMD

if you really want it set up as "right" as low lowered and stretched anything can be,
call GMD.

Peter can measure all the angles for you and give you suggestions on where you should go. I do not speak for Peter, but just don't call and ask him a bunch of questions, he will really need to see it and measure it.

....and I'd double check your tire pressure gauge.

best of luck

[timmyho414]

look, I'm not trying to be a dick.

I give you credit for actually measuring your rake and and asking questions. There are a lot of people on here who knew a lot, more then me, who can help. You have to ask the right questions. You must also except that what you are doing goes against everything a lot of us have spent years trying to learn and become better at. With that said...

Tunertype summed it up pretty good.

1. check/set your sag, too much sag and it can bottom out, causing a harsh ride.
2. check/set your rebound, too fast on the rebound can cause a harsh ride. It's like riding a pogo stick. you hit a bump and the bike will try to bounce you off the seat.

you said you already did this...what are your numbers?

my money is that they are way off, on the rear anyway. If they are and you can't get them where they should be you need parts, expensive parts and expensive set up time.