Wheel swap on GS550.

[yorkshireracer]

I'm building a Post Classic GS550 race bike and am swapping to 17" wheels, already in process of fitting an FZR 400 back wheel.
Does anyone have any idea what 17" is likely to fit the front with the minimum of grief. I really need to keep the original forks, so was thinking something off a modern 250 may go.
Any help would be great. Thanks.

[hjfisk]

Why not the FZR front, no matter which you choose you will have to get creative to fit a brake to it using your original forks, an Kawasaki EX 500 has a single disc front wheel also, or a GS 500, are you planing on single disc or dual ? It will all depend upon what you have room for and what the rules will allow for up grading.

[yorkshireracer]

I'm sticking to dual disc but looking at uprating to Lockheed calipers. Rules are basically open for brakes / wheels.
Bike is pre '82 BUT I could uprate the front end to something pre '89 as I'm racing one series mixed in with pre '89. Just don't want to go down that route at this stage due to cost.

[GregT]

If you're keeping the 550 forks, your main criterion is width across the disc mounting faces. It's a juggling act to fit twin piston calipers in and still have clearance to the wheel spokes. Lockheeds are great but the 08 Brembos are just as good - when used with a 14mm master cylinder - and a fraction of the price too.
If you need to sort out disc bolt pattern and offsets, Metalgear website is very useful - but so far they don't have a search function by diameter...

[yorkshireracer]

Brakes are already twin piston and it's on mag not spoke wheels (all standard stuff )
Can't use Brembos as they are too modern, as to be pre 89 and the new Lockheeds are a direct copy of the original calipers.
I've got eye on a GSXR 250 that should fit and I'm also going to try a 600 Bandit as well so hopefully problem solved.
I'll post the results.

[GregT]

The "08" Brembos are a model designation - not a year. They were used from the very late 70's up till very recently. Opposed piston and as i said, cheaper than Lockheeds.
Our GS1000 racebike in the SI uses them and hasn't been out braked yet - even against pre 89's....though most of that is the rider....

Spoke clearance..some of the 3 spoke mags have uncomfortably fat spokes which in concert with narrow forks makes fitting opposed piston calipers...difficult.

[yorkshireracer]

Ha, thanks for that, I'll look into it a bit more.Didn't realise you were here !
Apart from Postie club everyone runs everything in pre 89 in NI so it's all bleedin' ZXR 400's, clearly I'm going to have to catch 'em on the twisty bits. We know were that's going to end up

[GregT]

Yeah, well, I've suggested you come South....
Don't talk to me about B..... ZXR400's - there's a couple running down here which give us trouble...one major problem is their habit of passing bigger bikes under brakes then moving over and taking the line...leaving the rider of the big and underbraked pre 82 to find a way of avoiding disaster....They've learned not to try that on Kev as (1) he'll punt them off....and (2) he's braking as late or later than them....
The last meeting at Levels Kev did before going back to Oz, he beat the quickest ZXR 3 out of 5 races...starting off the back of the grid, and if there'd been a prize for entertaiment value he'd have won that...sideways into turn one every lap.

Pic of our current front brake setup - 296mm discs on centers I machined up - and using Brembos of course.

[GregT]

Finally found this pic of the last outing at Levels - shows the ground clearance differences between a modern and the GS quite clearly....
The new motor is around 40mm shorter on the left....
And yes, as i said, Kev got him good.

[mawg]

This may seem like a stupid question,and if so let me apologize in advance, but why do you need to keep the original forks?The reason is ask is cause 86- 88 GSXR forks will bolt right in, giving you four piston brakes with 18" wheels, though you"ll loose some ground clearance.

[hampshirehog]

Why not get hold of some GS750 spoke wheels (19") and change to 17" rims.

[fast pom]

Why not get hold of some GS750 spoke wheels (19") and change to 17" rims.

They are rearer than rocking horse sh#t down here , and if you can find a pair will cost you big time.

[GregT]

They are rearer than rocking horse sh#t down here , and if you can find a pair will cost you big time.

Unfortunately true...but conversely, there's quite a bit of Z1 spoke wheel stuff around here. That or later 2 stroke disc/spoked wheel hubs is what I'd use if I wanted spokes.

Forks - the OP is talking a pre 82 racebike for which he must use period forks...not necesarily Suzuki, but correct period.