What to do with new wheels?

[KWACKERZ1]

I have a few ideas regarding upgrading my wheels to run wider tyres and rims,
so as loads of people must have gone down that route I thought I would ask for some input.

If I build some wider spoke rims what are the largest sizes I can get away with running on standard swing arm and forks?

If I go this route should I go 18" front and 17" rear or 18/18.

(Whats the best tyres for this setup, I know the earlystocks boys run avons)

or should I go 17" front and rear.

Anybody who is out there running 17"s what's the ground clearance like.

I am also looking at putting together a special (eventually)with a wider swing arm and 17" rear What is the widest anyone has done using an offset front sprocket.

Input and comments would be greatly received as it could save me time and expense.
Cheers
Phil

[Pigford]

Hi matey

I'm using Gixxer running gear (17" wheels, 120/70 front & 180/55 rear).

The 180 is a tight fit at the engine sprocket bit. The sprocket cover needed a little bit filed out to clear the chain. I'm using a 630, so a switch to a 530 would be better.



The off-set sprocket is a Debbens billet item although Talon (Yeovil) do one off stuff too.

Riding, handling & cornering all OK, so GO FOR IT

[KWACKERZ1]

Thanks for that thats just one question are you running standard lenght forks, or gsxr items?
Cheers
Phil

[debben1]

Hello KwackerZ1, I have rebuilt my Z1000 rear hub with a 6" rim and a 180x17 Shinko tyre, this rim needs to be offset to allow the chain to clear the tyre and then refit the wheel back into the centre line of the bike by fitting the hub over to one side. to do this you need to fit a wider swing arm and an offset motor sprocket, the 5/8 offset sprocket with a 530 chain gives enough clearance.
The widest rim you can fit without fitting an offset sprocket is 3.5" but this will not fit in the stock swing arm with the chain adjusters pulled forward.
Which ever wheels the first job is to ensure that the front and rear wheels line up, so many we see do not. Once you have the wheels aligned you can run a straight edge (long straight tube will do) off the face of the rear sprocket to see how much the front sprocket needs to be offset, sometimes it is possible to machine the rear sprocket carrier to move the chain line in.
The frame tubes will limit how far you can offset the chain line and therefore how wide you can go with the rear wheel, unless you run the chain on the outside of the frame tubes. The frame tubes are 240mm apart which gives a centre line for the wheel at 120mm, but as you need the width of the chain (non O ring 530 is 23mm) plus at least 1 mm each side for some clearance you need to allow a minimum of 25mm both sides of the tyre.
So with 120mm centreline for the rear wheel minus 25 mm you have a maximum 95mm centre of wheel to the edge of the tyre.
Regards, Steve

[debben1]

300mm wide rear tyre

[Pigford]

Kwackerz1, I'm running later model (shorter) USD forks. The yokes are off-sett a bit, but in an ideal world the earlier ('90 - 92) USD forks would be better as they're a good inch or more longer


One-off billet yokes help

[chrisu]

this is what the longer GSXR forks look like.

[Pigford]

Kwackerz1, try to ignore Chris's dodgy PURPLE paint work

[KWACKERZ1]

Pigford, Chris, Steve,
Excellent food for thought and very comprehensive. (Had to read Steves again tonight when I was more sober, as the first time it passed me by)

Both Chris's and Pigfords bikes look cool, (even with the purple) very nice.


I think I will do two things,

1. Get a wider swing arm for my a1 and respoke the wheels to 17" ones.
running standard forks.

2. Build my project with a zx7r front end I already have and get a swingarm made for that to take the marchesini I have.

SO my next question is, who do I get to make me a new stem, as I already have a set of zx7 yokes but the stem length will need altering.
further suggestions anyone? thanks again

[Ed Z1-R]

KWACKERZ1, You could try Graham at Pegasus Engineering. He does a lot of one off stuff and is a biker himself.
Pegasus is based in Coventry, you can contact Graham on 02476678518.
Hope this maybe of help.

[KWACKERZ1]

Will do thanks.

[Pigford]

Kwackerz1, get an old standard yoke (that fits ur frame) and a good engineer can use the stem to suit the set of yokes that fit the forks
Mix & Match

[debben1]

Hello KwackerZ1, Regarding fitting the ZX7R front end , the ZX750J, K, L, M and P all use a BRG1232 steering bearings where as you will need to fit/use the BRG1231 steering bearings, so as Pigford has suggested fitting the original stem to the ZXR yolks is worth considering, but you also need to check the final ride height, the forks from the ZX7R are about 720mm where as the Kawaski Z900/1000 forks are around 780mm, loosing this 60mm along with 50mm lost in swaping from 19" to 17" front wheel, give's a front end drop of 110mm. not only will this dramatically reduce ground clearance for cornering but will steepen the steering head angle which could reduce straight line stability. You will also loose some of the steering lock as the wider diametre forks will require larger steering lock stops to prevent the tank being hit on full lock. doesnt sound like a big deal but after years of pushing specials around the workshop in a 22 point turn you start to wonder about the benefits, ie a bike that once had plenty of steering lock, ground clearance and straight line stability has been converted to one that hasn't. The suspension on later bikes is technically better but perhaps only when fitted to later bikes where the steering head is mounted much lower. Steve

[Pasc]

Zx9r usd's are a couple of inches longer than the 750's if it helps.

[KWACKERZ1]

Thanks guys, (The bearing nos are useful) I have already considered the fork length problem and maxton can lengthen the forks as they have done this on many others (although not zx7's).
The other alternative is izax engineering can do offset yokes but both options run into the ?400+ bracket.

I appreciate what youre saying Steve about the steering lock, I have recently built a street fighter and nearly crashed it the first time out due to it having the same lack of steering lock it had as a race bike.

I must admit I am starting to wonder if the wider tyres better suspension route is worthwhile, or just go slightly wider, on the rear, fit an 18 front and a fork brace. But when I have a complete front end with brakes and a set of marchesini's it seems a shame not to use them.

I'll have to have a dry run and see how we go.
Phil