Rear tire conversion

[Guest]

Converting my 1100E rear wheel to an 85 GSX-r 750 rear wheel. So far all is going well. My friend is helping me CNC an adapter for the old brake disk to work with the new wheel and still utilize the old caliper as well.

Rim centered up nicely with no spacers on the left. Cut the original 28mm left spacer down to 26mm and it spaced the right side of the axle nicely.

Over all I need 16.5mm of offset to get the chain to work. This is .5mm over 5/8" but I'm thinking 5/8 offset on the front will put my chain into the frame and left shock. Since both front and rear sprockets are 8mm wide I'm considering making my own offset sprockets for both front and rear and then getting the .5mm remaining by spacing behind the front sprocket.



Would like to know if someone has put a 5/8" sprocket offset in one of these just fine without having to clearance the frame or move the shock. I'm assuming my wheel has to stay centered. Not an engineer or physicist but I'm thinking so.

[niclpnut]

I have ran into problems with a 530 chain and 5/8 offset sprocket in regards to frame clearance.

Alot of ppl doing the conversion go with a 520 set up and it eliminates alot of the clearance problems.

Nic

[cdnoel]

520,530 chain.

Probably going to stick with my 630 as I'm looking into more HP's. A 520 would only give me a 16th more though, I think.

[Big T]

Go with a 3/8" offset front from PBI
and shave the sprocket carrier to match

[hjfisk]

Yes 3/8 off set and shave the carrier. That is what I used on my 1000. I also went to a 530 chain, and could have gone to a 520. You claim you are looking at more HP , the new chains will take it. There are late model 1000's out there running 520 chains no problem and they are 150hp plus off the floor. You will have to do some very serious mods to get there.I wouldn't worry about the chain , just buy a quality name brand, high end one.

[cdnoel]

No meat at all behind the sprocket carrier

No meat at all in the castings behind the rear hub sprocket carrier. Parts from these things were made to be light weight as even the spokes are much thinner though they look much the same as 82-85 GS spokes.

Trying to stay as stock looking as possible. Going for the show but no go look . Shooting for about 160hp at 1229cc's. Notice the extra motor in the background of the photo. If I change my mind on the show look I also have a spare body set rattle canned flat black with 750 badges.

Would much rather go with a non modified rear sprocket as custom will be a maintenance pain but it's looking like the way to go.

Have so far an 1150 crank with matching billet clutch basket and straight cut gears. Stator rotor included. Will start a thread on that one when I open up the motor.

[Big T]

Just shave the outer face of the sprocket carrier, it only takes 4-6mm

[CivilRock]

How wide is that 85 GSXR rear wheel?

Mine is a 92 GSXR1100 rear and it's 5.5" wide. You're going to need every mm of space if it's the same size. I had to buy a new longer chain anyway, but I would venture to say that a modern 520 chain is at least 2x stronger than a 1982 630 chain. Just better materials.

I used the old sprocket and spacers with a cheap $14 530 countersprocket and made it work. But it will take a grinder and a welder.
Maybe you don't need a welder, but it's added insurance/strength.

Check out page 4 of my website for more info: http://www.civilrock.com/GS1100EZ/4

[cdnoel]

GSX-r Rear wheel.

The GSX-r wheel I have is an 85 and all 85-87 GSX-r 750 rear wheels are 18X3.5" , 3.5" being the bead width. They are also the only GSX-r wheels I found with a similar to GS spoke pattern as this is important to me. Here are a couple of pics of the progress I have made so far. The brake disk required me to have a friend CNC an adapter for me but the other alternative would have been fitting a GSX-r caliper to go with the GSX-r disk. The offset ended up being 3.5 mm compared to the original having about 12mm of offset.

to fit the GSX-r rear sprocket I did have to shave 4mm off of the hub to sprocket surface. This is where I admit "you were right" to Mr. just do it. This was because the bolts ran into the swing arm and the chain was scary close to the rear shock. 4mm later and all is fine.

Anyways, I have a 3/8 offset front sprocket with two original sprocket washers behind the sprocket and two in front. This gets the chain lined up spot on. The chain guard unfortunately didn't make it.

[cdnoel]

pic two.

Here's the other pic.

I have converted from 630 to 530. This lead me to believe I had to convert the diameter of my 42 tooth 630 to a comparable 530 diameter of 49 tooth. After money spent and numbers crunched my engineer buddy told me that if I had just stuck with the same number of teeth both front and back the conversion would have been done for me automatically.

I suppose this is why I dropped out of engineering classes with intro to engineering. I digress...

How wide is a 160 rear tire? I've got just about 6" of real-estate to play with.

[Steve]

After money spent and numbers crunched my engineer buddy told me that if I had just stuck with the same number of teeth both front and back the conversion would have been done for me automatically.

That is when you point out to your engineer buddy that the new sprockets with the same number of teeth will be smaller, and the chain would then be hitting things like the top of the swing arm. You need to maintain the same diameter, not necessarily the same tooth count.

Your 42-tooth original sprocket should be replaced with a 50-tooth sprocket. Don't forget to also 'do the math' on the front sprocket to maintain the proper ratio.

.

[cdnoel]

math done

Did the math on front and came up with 18 for front instead of 15. The 42 converted to a diameter between 49 and 50 so i decided to go with the slightly taller gear. The old set up seemed to top out too soon. We did conclude that the larger diameters would also handle the torque a little better.

[tom]

Here's the other pic.

I have converted from 630 to 530. This lead me to believe I had to convert the diameter of my 42 tooth 630 to a comparable 530 diameter of 49 tooth. After money spent and numbers crunched my engineer buddy told me that if I had just stuck with the same number of teeth both front and back the conversion would have been done for me automatically.

I suppose this is why I dropped out of engineering classes with intro to engineering. I digress...

How wide is a 160 rear tire? I've got just about 6" of real-estate to play with.

well its 6"1/4 wide on my 4.5" wide wheel

[cdnoel]

3.5?

Ah. I was thinking I might be being a little ambitious trying to get a 160 on a 3.5" bead. I can get the extra 1/4" by moving the bar that holds the caliper in place over. I know I've seen 160's on these rims but that doesn't mean they were correct. I'll Have to check into this before I put too wide of a tire on this rim.

[Big T]

Indeed you do

a 3.5 rim is good for 140-150 tire

You need a 4.5 or better a 5.5 for the bigger tire