GSX1100G rake fix?

[Guest]

I'm hoping there may be a few engineers or modifiers here that may be able to help out with an idea of fixing the weird rake Suzuki gave the 91-92 GSX1100G.
According to this site http://www.motorcyclespecs.co.za/model/suzu/suzuki_gsx1100g 91.htm the GSX1100G has a rake of 32 degrees and a trail of 156 mm.

I have an 07 GSXR750 that I had parted out and still have the front forks and triples. According to this site http://www.motorcyclespecs.co.za/model/suzu/suzuki_gsxr750 07.htm it has a rake of 23.8 degrees and a trail of 97 mm.

Would the 750s USD suspension help fix the chopperish steering of otherwise an awesome bike?

 

[RichDesmond]

Not very much. If the triples have more offset the trail will be reduced some, but the main issue is the steering head angle. The solution is cutting the steering head off and rewelding it on so that the rake is reduced.
A fairly common mod in superbike circles in the late ‘70s-early 80’s, but not for the faint of heart.

 

[Guest]

Not very much. If the triples have more offset the trail will be reduced some, but the main issue is the steering head angle. The solution is cutting the steering head off and rewelding it on so that the rake is reduced.
A fairly common mod in superbike circles in the late ‘70s-early 80’s, but not for the faint of heart.

I thought of that, but had hoped that there was an easier way without altering the frame. I know there are some triples that have an angle built into the triples, but I don't have a clue to which bikes do, other than cruisers which I think the angle would be going in the wrong direction to help quicken the steering. I think I heard here that adding USD forks to our bikes, the GS models, brings the wheel too close to the head pipes, so I figured that it may do the same with the GSX.

 

[RichDesmond]

...I think I heard here that adding USD forks to our bikes, the GS models, brings the wheel too close to the head pipes, so I figured that it may do the same with the GSX.

Yeah, but that's actually going the wrong way. If a fork swap brings the wheel is closer to the pipes that means the triples have less offset, which means more trail.

It gets a little confusing, but more rake=more trail, more offset=less trail, lowering the front=less trail.

Trail is really what matters, the other parameters aren't that important in and of themselves, but only in how they affect trail.

The other thing you can do is raise the rear a bit with a longer shock or different dog bones.

A more expensive option is custom triples. I had a machinist friend make some up for me when I was racing SVs. Because it was a buddy deal it wasn't stupid money, but still not cheap.

If you do any of this stuff I'd suggest calculating your actual trail first so you know what you're really working from.

 

[Guest]

I found this bike doing google image searches. It is located in the Ukraine. He said he used a 93 GSXR 750 forks and it looks to have brought the front wheel in quite a bit. Not sure if the trail was changed, but I think it has. Looking at the first and third photos, it looks like the angle of the forks may have changed and judging by looking at the way the tank has an angle to it now, the tail was raised some also or it could be that the front forks are shorter. Either way, wouldn't this help quicken the steering?

Original bike

Photo shop image

Finished bike with the 93 forks. I see he can still use the stock wheel to match the rear.

The 99-00 R1 tail looks good on there.

 

[TxGSrider]

Maybe find someone to machine offset bearing carriers to fit in the head, then use a smaller OD bearing that would fit inside of them?

 

[Guest]

I thought of that, but had hoped that there was an easier way without altering the frame. I know there are some triples that have an angle built into the triples, but I don't have a clue to which bikes do, other than cruisers which I think the angle would be going in the wrong direction to help quicken the steering.

You are confused as to what rake and trail are. Rake is the steering head angle and it is solely determined by the steering head angle off vertical (the steering head is where the triples pivot in the frame), the triples have no effect on it. Angled triples affect the trail, which is the distance the contact patch sits behind the intersection point of the steering head axis and the ground. Your GSXR fork and triples will not change the rake angle at all and will result in a significant increase in trail, which will give heavy steering and likely some weirdness at low speeds.

You can slightly change the steering head angle with ride height adjustments front and rear, but that is limited to small changes of no more than 1 degree or so. To radically change the steering head angle you are stuck with altering the frame as Rich has said. On your bike that would be a difficult project as the steering head would have to move forward several inches to achieve a much steeper rake angle while avoiding header to wheel interference. Going from the 32 degree angle to 25 degrees would move the steering head forward over 3", assuming a fork length of 30".

The easiest way to fix the chassis geometry of the GSX1100G is to buy a bike that has what you want in the first place.


Mark

 

[Guest]

You are confused as to what rake and trail are. Rake is the steering head angle and it is solely determined by the steering head angle off vertical (the steering head is where the triples pivot in the frame), the triples have no effect on it. Angled triples affect the trail, which is the distance the contact patch sits behind the intersection point of the steering head axis and the ground. Your GSXR fork and triples will not change the rake angle at all and will result in a significant increase in trail, which will give heavy steering and likely some weirdness at low speeds.

You can slightly change the steering head angle with ride height adjustments front and rear, but that is limited to small changes of no more than 1 degree or so. To radically change the steering head angle you are stuck with altering the frame as Rich has said. On your bike that would be a difficult project as the steering head would have to move forward several inches to achieve a much steeper rake angle while avoiding header to wheel interference. Going from the 32 degree angle to 25 degrees would move the steering head forward over 3", assuming a fork length of 30".

The easiest way to fix the chassis geometry of the GSX1100G is to buy a bike that has what you want in the first place.


Mark

I'm no expert, but I don't think I'm confused to the difference of rake and trail. What I don't know, is how much is needed to help the situation of the GSX1100G. I'm not trying to make it into a modern bike or a sport bike and I have plenty of other bikes that are completely different. I'm just trying to help this bike steer better.

I have no idea if the 93 GSXR 750 triples have the same offset or angle as the GSX1100G triples, that is why I'm asking. The example provided where the guy used a 93 GSXR 750 front suspension was used for some purpose, but I cannot get the link to his build thread to open, to find out if it was something he had lying around to use or if it was a researched solution to a well known issue with these bikes. :indecisiveness:

Someone here recently showed his 80-81 GS1100E with TL1000 triples and Busa USD forks. I'm not sure why he didn't use the Busa triples along with the forks, but my guess it that the TL triples had a different angle than the Busa an gave a better trail than just using the whole Busa suspension, but I'm just guessing. I do have an '07 GSXR 750 that I can use if it will work, but then it wouldn't give me an ability to mount the speedo drive , which looks like the 93 has.. Plus the axles of the later bike wouldn't allow me to keep the stock front wheel.

 

[GS1150Pilot]

I think the GSX1100G is a bike that is better left as it is. Trying to muck about with that will also possibly affect things at the rear, which as a shafty, is already a sensitive issue. The GSX is a freight train, not a sportscar.

 

[Guest]

I think the GSX1100G is a bike that is better left as it is. Trying to muck about with that will also possibly affect things at the rear, which as a shafty, is already a sensitive issue. The GSX is a freight train, not a sportscar.

Have you ridden one? It's a great bike, but for the steering. Like I said, I'm not trying to make a canyon carver out of it, but it would be nice if it was a little more responsive.

 

[GS1150Pilot]

I haven't, but I really like them. I think of them as a modern GS1100G with a little more Cadillac built in.

 

[Guest]

I haven't, but I really like them. I think of them as a modern GS1100G with a little more Cadillac built in.

They don't have the same steering feel. The GSX has a weird chopperesk geometry. Not sure why they did that, as I have never ridden another bike that wasn't a dedicated cruiser with something similar. Dave (Portdave) is looking at one in Port St. Lucy and is also interested in trying to come up with an idea to correct the steering feel some. We know what it is and we are not trying to make into something that it isn't, just a little better than it already is.

 

[GS1150Pilot]

I think the VX800 has a similar geometry. It's of the same vintage as the GSX.

 

[RichDesmond]

Triples don't have an angle (with very rare exceptions).

 

[Guest]

I'm no expert, but I don't think I'm confused to the difference of rake and trail. What I don't know, is how much is needed to help the situation of the GSX1100G.

OK. It sounded like you were talking about changing the rake angle with angled triples, which is not possible. All you can change is the amount of trail and I don't think you are going to improve much with small changes there.

As Rich says, the vast majority of triples are not angled at all, they place the forks parallel to the steering stem with an easily measured offset number so all you can play with is differing offsets.


Mark

 

[Buffalo Bill]

Not very much. If the triples have more offset the trail will be reduced some, but the main issue is the steering head angle. The solution is cutting the steering head off and rewelding it on so that the rake is reduced.
A fairly common mod in superbike circles in the late ‘70s-early 80’s, but not for the faint of heart.

There's your answer Rick. Plain and simple.
Rig up a jig, cut the frame and reposition the steering head (with the forks and wheel attached), until you find the ideal rake angle. Then come up with a plan and good welder to finish it.

 

[Guest]

There's your answer Rick. Plain and simple.
Rig up a jig, cut the frame and reposition the steering head (with the forks and wheel attached), until you find the ideal rake angle. Then come up with a plan and good welder to finish it.

Not so plain and simple. Like I said I'm not looking to do major altering, just some minor tweaking to make it better than it is. If I can accomplish this and get a better suspension, that's a win win. There is a 96-99 GSXR 750 suspension on eBay that is located in Orlando, so I could save the shipping, but he still want's $340 for it and I'd have to work out a different bar setup as my back and wrists can't handle the lean for more than 20-30 minutes. https://www.ebay.com/itm/1996-1999-...842050?hash=item3d72e87542:g:GLUAAOSwNeVbgaTW

 

[GregT]

There's your answer Rick. Plain and simple.
Rig up a jig, cut the frame and reposition the steering head (with the forks and wheel attached), until you find the ideal rake angle. Then come up with a plan and good welder to finish it.

Or run it into a wall....

 

[Guest]

Or run it into a wall....

Well aren't you clever, I'll let you keep that technic in Australia.

 

[Guest]

Not so plain and simple. Like I said I'm not looking to do major altering, just some minor tweaking to make it better than it is.

In that case jack up the rear 3/4"-1", drop the front 1/4"-3/8" and call it a day. Changing the forks is a waste of time and won't do anything useful for you. All of the sport bike forks have minimal offset to work with 23 degree rake angles and will result in way too much trail on a 32 degree steering head.


Mark