GSXR Rear brake mount question? - Thanks

[mlaalm]

Getting ready to switch out my stock GS1150 3.5 inch rear wheel with 130/90/17 bias-rubber for a 1987 GSXR 3.5 inch with 160/60/18 radial. I wanted to go with the 18 inch rim to offset going with the lower profile rubber.

Question - Is it possible for me to use a stock 1987 GSXR rear brake MOUNT (that mounts under the rotor) and swing it around to mount my stock GS1150 rear caliper in its normal (upper position).

I know it sounds complicated but I'm trying to see if I need just a mount or a complete rear GSXR mount and caliper assembly as well as brake arm.

The GSXR rotors are alot smaller than the GS1150 rear rotor. Any help appreciated. Thanks in advance

Mike

 

[Basket Case]

There's a lot of things to look at with that kind of change. I know it's not specific to your request, but I feel like typing it anyways

I'm assuming, by your request, that you're planning on using the original swingarm. A big thing you need to check is that the tire isn't going to rub on the swingarm. The radials tend to be wider, and you may see a problem there right off the bat.

You're stock caliper won't work with a smaller brake disc. IIRC, It's not the mount arm that controls the distance the pads are from the axle, which is where your problem stems from. I'd recommend one of two things:

1: Find out if a larger brake disc will fit on that wheel, so that you don't need to change the location of your stock caliper.

2: Look into changing to a new complete swingarm assembly (that fits that bike). Mix and match stuff is tough to get right.

Of course, I could be wrong, and the next poster could contradict me I haven't done this conversion on a GS before, but I had those problems fitting a FZR-400 rear wheel to a GPZ-550.

EDIT: Or refer to the "gsxr conversion parts and upgrade answers" thread that's just started. Great writeup on this conversion by someone who's actually done it. (I was pretty close on what I said, though)

 

[RJ]

I had to overcome the same dilemma on my '82 1100E. I was able to fit a 5.5 x 17" wheel with a 170 series tire from a '92 GSXR 750 into my stock swingarm using the GS spacers and a GSXR caliper hanger. I did swap out the GSXR sprocket carrier for the GS unit as the old one is narrower and gave me more clearance for the chain (which was converted to a 530 series). The GS brake rotor won't mount onto the new wheel, so I used an RF 900 rotor. The caliper is a Hayabusa unit. The caliper will only work in the upside down position due to the placement of the bleeder valves and the mount braket that is part of the caliper body casting and cannot be removed. If you try to use right side up the bracket points backwards, and the caliper wont line up properly if you flip it around. That means the swingarm needs to be modified to have the caliper bar mounted on the underside. I assembled everything together on the rear end, swingarm and all, and took it to a welder. With the caliper bar attached to the caliper I was able to show the guy exactly where and at what angle I wanted the bracket to look like on the underside of the swingarm. $65 later everything works like a charm.
Unless you can mount your old rotor to the new wheel you will need to do something similar to what I described. As far as room for the tire I don't think you're going to have a problem. Like I said I've got a 5.5 incher on my bike.

 

[Guest]

Thought 87 rear rims were 4.0"? My rear is 4.0", although it is an 1100 rim. Wouldn't a 160 series tire be a bit wide for a 3.5" rim??? RJ has it right. I am having to do the same thing...just make some meausrements and take the swing arm to a competent welder to make a mount on the underside of the swing arm.

Good luck!!\\/

 

[mlaalm]

Sorry I was assuming it was a 3.5 I'd be happy with a 4.0 inch. I'm still waiting for the wheel to come in the auction I listed below is from where I won it. He is also going to send me the rear caliper mount

I'm really hoping I can spin the caliper mount 180 degrees to the 12:00 position and mout up my stock GS1150 caliper to the GSXR mount (hopefull the holes will match up) Seems like I may be hoping for too much tho.

I have a 88 GSXR1100 4.5 with a 170 / 60 that WILL NOT MOUNT. I hear the 160 series will work but I'm not sure if anyone has done it with the 18 inch GSXR wheel. I guess I should have played it smart and went with the 17 inch Katana stuff but I am really wanting to mantain as much ground clearance as possible (sounds crazy I know) And I don't want to extend the swingarm.

Thanks for the assistance. I will post a pic or two when it is complete
Mike

http://cgi.ebay.com/ebaymotors/ws/e...=1&item=4635658180&sspagename=ADME:L:AAQ:US:1

I felt I did good on the rim with useable rubber on it

 

[Billy Ricks]

I used my stock caliper stay when I swapped. Bent the arm a bit to clear the sidewall and cut the mount off the top of the swingarm and had it welded back on underneath.

 

[mlaalm]

I used my stock caliper stay when I swapped. Bent the arm a bit to clear the sidewall and cut the mount off the top of the swingarm and had it welded back on underneath.

I will be able to use the stock GS1150 mount but it has to be modified to fit the small area that is left after the 86-88 GSXR wheel is installed. I trimed the stock mount down to fit the remaining space (trimed it on the swingarm side only) and now I will have it cut and lowered (behind the swingarm so it does not show) to hug the rear GSXR rotor better.

I have a GSXR mount but I did not want to modify because I will probably have enough added to the swingarm this winter to mount up a 5.5 Bandit Stright Spoke.

The 87 GSXR 750 rear I won off ebay with the 3.5 rim and 160 rubber did not look right and I'm not even sure how the guy had such a large tire mounted on a 3.5 inch rim. I also already had a 1988 GSXR1100 4.5 that the 160 fits on 'real nice'.

The whole 86-88 GSXR 18 inch rim setup on a GS1150 is a 'slight pain' in hindsight I should have just put a newer style Katana stright spoke 17 incher on it and been done with it (but I keep having issues with wanting to keep as much clearance as possible). Putting the 18 inch on the GS1150 pushed the rubber even closer to the front of the swingarm of which there is not alot of room to begin with. I really wish Suzuki had made the GS1150 rim as easy to upgrade as the GS1100 rim.

Once I go with the 5.5 inch I will make up the the difference with a PCO V&H or some sort of sidewinder exhaust vice my MAC System. The X-Pipe in black is acutally looking kinda interesting, especially since baffles are included.

Anywho thanks for the input. Lesson learned for me on the GS1150's is stick with the Katana 4.5 inch wheel upgrades on a 'stock swingarm'.

 

[mlaalm]

Its nice having radial rubber on both ends now

 

[Billy Ricks]

Its nice having radial rubber on both ends now

Radials are superior in every way compared to bias plies. They roll with less resistance, they're lighter, grip better, and soak up bumps far better than bias.