Gsxr Forks On Vtec?

[Baileyrock]

I have a possible Vtec track bike project (see other post) and wanted to know if anyone has or knows what I would be dealing with trying to run 07 GSXR 600 forks on a Vtec?

These are 738mm long, have 50mm upper tube size and 53mm lower tube size and large axle.

Any thoughts on what could/would work?

[Guest]

many people had swapped older gixxer's forks on Firestorms... not so different bike from Vfr

I think you can find lots of measurements on R1/RC51 fork swap topics

btw, very good mod, if possible :cool:

[Guest vfrrider]

I think the main problem is that the modern GSXR forks are very short in comparison. Find the relaxed distance from triple to axle and compare.

Larry

VFRrider

[SEBSPEED]

If you decide they're not too short, you'll probably end up pulling the stem from the gixxer lower triple and replacing it with the stem from the VFR. Check both those parts out and see if they're close in diameter, for starters.

[Baileyrock]

I think the main problem is that the modern GSXR forks are very short in comparison. Find the relaxed distance from triple to axle and compare.

Larry

VFRrider

Yeah, in this application I'm not worried about the shorter forks(33mm shorter) as I would be running clip-ons under the top tree for the typical tuck down track bike or top mount handlebars for an upright Tuano(?) set-up.

[VFR800R]

I haven't heard of GSX-R600 K6/K7 forks done, but of course there are some similar swaps out there:

Swiffer's New Front End featured GSX-R1000 K1/K2 forks, which are shorter than your 600K7 forks, so the length problem doesn't seem to be insurmountable. And of course there are some CBR swaps out there, and those forks are very short. You're using these for a track bike anyway, so low clip-ons will be a benefit, and short forks will help reduce some of the increased trail you will get from CBR929RR/954RR or RC51 triples.

[Here (Definitive GSX-R Fork Swap Chart) is an excellent source of data for GSX-R related fork swapping, with more numbers than you can shake a fork at.]

I believe your main issue will be with the lower triple tree; the most popular choices for inverted-fork swaps (CBR929RR/954RR and RC51 SP1) use a 54mm lower fork diameter, where your 600K7 is 53mm. I don't think you would want to just bolt them together, but I'm sure you could make a thin shim to take up the difference.

Personally, I have a set of ZX-10R forks in my closet that are waiting on a few more parts before they can be bolted onto my VTEC. Good luck, BR!

Lacy

[Baileyrock]

Good stuff Lacy, thanks! :cool:

[Baileyrock]

Any other input with GSXR forks? These are 738mm long on the 07 where the earlier ones were only 720mm.

So are the 929/954 triples 50mm on the top and 54mm on the bottom tree? All Honda's this way?

[The Phantom]

BR, yes the 929/954 triples are 50/54mm, as are just about all Japanese USD combos. I believe Triumph and Ducati also use these measurements.

I'm very surprised to see that Suzuki went to 53mm for the lower triple on the 07 GSX-Rs - most manufacturers have virtually standardised sizes as most of them buy from the same suppliers, eg. for radial brakes the mounting bolts are 110mm apart for most bikes (whatever that is in miles). I have both ZX-10R and R1 lowers and can confirm that they are 110mm, and the forks are definitely 50/54mm.

I'd ask someone like BLS about a shim to use the GSX-R fork in a 54mm lower triple - it can probably be done, but get the right opinion first.

738mm is fairly short. It's not just the bar location you need to consider - ride height could be a problem with short forks, for ground clearance and also rake, which could get a bit twitchy with very short forks that steepen fork rake considerably.

That GSX-R chart page that Lacy posted is amazing; JZH was working on a similar thing for us. Interesting to see that they use 214mm fork spacing (which is what Honda used up to the 2008 CBR1000RR which went to 204mm) and also 207mm. R1 uses 210mm spacing, not sure about Kawasaki.

We need to get some specs on stems etc... I have an 04 R1 stem/lower triple somewhere, I'll measure it up.

Lacy, have you by chance looked into whether the ZX-10R stem/triples would go straight into the Honda steeringhead? I've been wondering about that for some time...

[Baileyrock]

BR, yes the 929/954 triples are 50/54mm, as are just about all Japanese USD combos. I believe Triumph and Ducati also use these measurements.

738mm is fairly short. It's not just the bar location you need to consider - ride height could be a problem with short forks, for ground clearance and also rake, which could get a bit twitchy with very short forks that steepen fork rake considerably.

Thanks Phantom!

Some simple .5mm shim stock should remedy the 1mm lower tree difference, not too worried there.

I don't see the 738mm length as an issue either as 41mm of the vtecs length is above the top tree which would make the GSXR fork about level with the top stock tree(actually 8mm above)and if I understand correctly the gull wing 929/954 tree would add another 30mm of exposed tube if needed. I would want to sharpen/steepen up the steering for track use, but this might already be handled with the offset of CBR triples? This is all what I need to figure out. Hell these sound long enough to use on my street VFR w/o issue by just using high rise clip-ons, but if my calculations are correct there would be 38mm of tube stick above a 929/954 top tree. :biggrin:

btw Suzuki looks like their using 108mm caliper mount spacing on these forks! :dry:

[SEBSPEED]

Kev, I can hook you up with some .020"(.5mm) aluminum shim stock if you need it. :biggrin:

[FotoMoto]

You can also add the 05-06 (I think any pre-08) CBR1000RR triples to the mix. They are the gullwing design but the upper is pretty ugly in naked form (has an electronic stablizer bolted to it). They also have the same steering neck length and bearings as the VFR. I'm using them with rc51 fork legs/brakes, wheel on my 4gen.

[shrek]

FWIW, we've been running that .5mm shim on the lower triple on the TL1000R (for those guys that chose to go with GSXR forks in the stock TL triples) for several years without a problem. Do you have an issue with the center to center spacing or are you going to make custom sized wheel spacers? Wouldn't it be easier as suggested above to press the VFR stem into the GSXR lower triple?

[VFR800R]

BR, yes the 929/954 triples are 50/54mm, as are just about all Japanese USD combos. I believe Triumph and Ducati also use these measurements.

I'm very surprised to see that Suzuki went to 53mm for the lower triple on the 07 GSX-Rs - most manufacturers have virtually standardised sizes as most of them buy from the same suppliers, eg. for radial brakes the mounting bolts are 110mm apart for most bikes (whatever that is in miles). I have both ZX-10R and R1 lowers and can confirm that they are 110mm, and the forks are definitely 50/54mm.

I'd ask someone like BLS about a shim to use the GSX-R fork in a 54mm lower triple - it can probably be done, but get the right opinion first.

738mm is fairly short. It's not just the bar location you need to consider - ride height could be a problem with short forks, for ground clearance and also rake, which could get a bit twitchy with very short forks that steepen fork rake considerably.

That GSX-R chart page that Lacy posted is amazing; JZH was working on a similar thing for us. Interesting to see that they use 214mm fork spacing (which is what Honda used up to the 2008 CBR1000RR which went to 204mm) and also 207mm. R1 uses 210mm spacing, not sure about Kawasaki.

We need to get some specs on stems etc... I have an 04 R1 stem/lower triple somewhere, I'll measure it up.

Lacy, have you by chance looked into whether the ZX-10R stem/triples would go straight into the Honda steeringhead? I've been wondering about that for some time...

I haven't looked into using ZX-10R stems/triples... I had thought about it to simplify the wheel and rotor spacing problem, but finally decided it was worth it to fight the spacing battle and have the ability to bolt up the ignition lock cylinder. Hence, I bought RC51 SP1 triples, but will end up using CBR954RR ones instead (the lower triple's gullwing shape doesn't look like it will accomodate the ZX-10R's positioning of the 54mm lower fork mounting surface). And I THINK that Kawasaki uses 210mm fork spacing, but I have not been able to confirm that anywhere on the Internet (and haven't had a chance to measure someone's bike).

I did A LOT of research on sizes to see what forks would fit, and I'll try to post the Excel spreadsheet I made when I get home from work. For example, Ducati does NOT use 50/54mm upper/lower triples; they use 53/53mm on their "standard" Superbike forks and 53/56mm on the Ohlins forks they use on their "S" and "R" models. Simple, eh?

Oh, and the Japanese use 108mm spacing for their radial brake mounting bolts, while the Italians (Aprilia, Ducati, MV Agusta) use 100mm. So be careful if you score that bargain set of monobloc Brembo take-offs from a 1098, because they won't mount up to your Japanese Showa or Kayaba forks. Although they will look pretty sitting on your garage shelf...

More to come this afternoon when I return to home base.

Lacy

[Baileyrock]

FWIW, we've been running that .5mm shim on the lower triple on the TL1000R (for those guys that chose to go with GSXR forks in the stock TL triples) for several years without a problem. Do you have an issue with the center to center spacing or are you going to make custom sized wheel spacers? Wouldn't it be easier as suggested above to press the VFR stem into the GSXR lower triple?

Hey shrek, long time no see! :blush:

Thanks, I'm not really sure about anything related to this project as it's exactly 48hrs old, so not a lot of homework done yet. Your right that if I could just press a Honda stem into the GSXR trees it would be easiest to just use the entire GSXR front end components(wheel, rotors, axle, spacers, etc.). :fing02:

I'm looking for the cheapest & easiest way to run it! :biggrin:

[vfrcapn]

Hey shrek, long time no see! :blush:

Thanks, I'm not really sure about anything related to this project as it's exactly 48hrs old, so not a lot of homework done yet. Your right that if I could just press a Honda stem into the GSXR trees it would be easiest to just use the entire GSXR front end components(wheel, rotors, axle, spacers, etc.). :fing02:

I'm looking for the cheapest & easiest way to run it! :biggrin:

I've got a RC SP1 steering stem sitting on the bench you can have. It should go right in to the VFR with the RC bearings. The lower threads are a bit buggered up though, you'd have to deal with that.

[VFR800R]

Hey again all,

Here is the fork swap spreadsheet I talked about a few posts back. It's nowhere near as exhaustive as the GSX-R one I linked to, but it covers a broader spread of forks.

Inverted_Fork_Swap_Data_Excel_2003.xls

It's saved in Excel 1997-2003 format, so if you need otherwise, let me know.

Lacy

[Baileyrock]

Got it, thanks! :blink:

[The Phantom]

I haven't looked into using ZX-10R stems/triples... I had thought about it to simplify the wheel and rotor spacing problem, but finally decided it was worth it to fight the spacing battle and have the ability to bolt up the ignition lock cylinder. Hence, I bought RC51 SP1 triples, but will end up using CBR954RR ones instead (the lower triple's gullwing shape doesn't look like it will accomodate the ZX-10R's positioning of the 54mm lower fork mounting surface). And I THINK that Kawasaki uses 210mm fork spacing, but I have not been able to confirm that anywhere on the Internet (and haven't had a chance to measure someone's bike).

ZX-10R forks definitely work fine in the 929 lower triple. I was hoping the fork spacing would be 214mm which would make the ZX-10R forks a very viable USD swap using 929 triples, especially the 2006+ forks which are only 12mm shorter than SP1 forks.

I did A LOT of research on sizes to see what forks would fit, and I'll try to post the Excel spreadsheet I made when I get home from work. For example, Ducati does NOT use 50/54mm upper/lower triples; they use 53/53mm on their "standard" Superbike forks and 53/56mm on the Ohlins forks they use on their "S" and "R" models. Simple, eh?

Oh, and the Japanese use 108mm spacing for their radial brake mounting bolts, while the Italians (Aprilia, Ducati, MV Agusta) use 100mm.

Gotcha, I took it to be 110mm with a quick check using a tape measure, tonight I dug out the digital verniers to confirm 108mm.

Great chart, thanks for sharing. My ZX-10R fork uppers are from a 2004/05 model. My suspension tech told me they were 10mm longer than the R1 uppers (which I don't have to compare, told him to ditch them as they were bent), as the chart lists 2004 R1 and 2005 ZX-10R forks as both being 730mm the ZX-10R must have shorter lowers... he did a little machining to make the R1 lowers go into the 10R uppers, overall length (on bike, unladen) is 755mm, and 735mm from axle centre to top of fork. The actual 10R upper is 490mm long (not including fork seal i.e. just the tube).

[Baileyrock]

OK I'm getting a little here as it looks like these GSXR forks may bolt right up to the Vtec with nothing more than a different upper bearing! The stem seems to be right length and the lower bearing is basically the same. One issue is that the upper tree on the GSXR is flat instead of the 929/954's gullwing set-up, so there would be no tube to speak of above the top tree for clip-ons.

Just have to figure out what the difference in triple offsets would do to handling, the VFR is 38/39mm vs the GSXR's 30mm(same as F4i).

Fun stuff, if it works it would mean I would just bolt up a GSXR wheel, rotors, axle, etc, no muss no fuss, otherwise I would use Honda triples and have to figure out all the wheel, rotor, spacing, axle, etc., etc. stuff. :biggrin:

[Baileyrock]

Anyone know of a good head bearing info source? AllBalls?? :biggrin:

[SEBSPEED]

Yeah, try the All Balls website (www.goallballs.com) and see what the part #'s are for the gixxer & VFR. You might just be the luckiest guy I know?

[vfrcapn]

Just have to figure out what the difference in triple offsets would do to handling, the VFR is 38/39mm vs the GSXR's 30mm(same as F4i).

You may just kick off a whole new round of frankenviffers with this. :biggrin:

I'm sure you're aware this will increase the trail significantly. On my VFR with the RC front end I raised the rear over an inch to somewhat compensate, along with actually raising the SP2 forks about 10mm. That seems to have mostly neutralized the additional trail. I can't say it's worked as well on the VF though. Do you know the offset of the RC triples in comparison?

[VFR800R]

RC51 and CBR929/954RR triples are 30mm offset. Same as your GSX-R, sounds like.

Keep in mind, Frankenviffers, that the GSX-R triples will not bolt up your ignition cylinder without some modification (probably just a simple bracket just to make it work), and the steering lock will likely never work. Which is fine on a track bike like BR is planning, but not so much if you're converting your streetbike.

Lacy

[Baileyrock]

Just have to figure out what the difference in triple offsets would do to handling, the VFR is 38/39mm vs the GSXR's 30mm(same as F4i).

You may just kick off a whole new round of frankenviffers with this. :biggrin:

I'm sure you're aware this will increase the trail significantly. On my VFR with the RC front end I raised the rear over an inch to somewhat compensate, along with actually raising the SP2 forks about 10mm. That seems to have mostly neutralized the additional trail. I can't say it's worked as well on the VF though. Do you know the offset of the RC triples in comparison?

Yeah, here are the numbers BLS sent me.

Stock VTEC 02 VFR

Rake 25.5º

Trail 95mm

120/70/17

Offset 43mm

VTEC with 30mm offset:

Rake 25.5º

Trail 109.3mm

120/70/17 (299mm)

Offset 30mm

Adjust the ride height on the VTEC and subract 2º of rake:

Rake 23.5

Trail 97.3mm

120/70/17

Offset 30mm

[vfrcapn]

RC51 and CBR929/954RR triples are 30mm offset. Same as your GSX-R, sounds like.

Keep in mind, Frankenviffers, that the GSX-R triples will not bolt up your ignition cylinder without some modification (probably just a simple bracket just to make it work), and the steering lock will likely never work. Which is fine on a track bike like BR is planning, but not so much if you're converting your streetbike.

Lacy

BTW, the value I had recorded for the RC51 offset was 32.5mm, I don't recall my source at the moment though.