XS650 Tire/rims Questions

[Vizzinzin]

Hi all, I've got a couple questions about tires & rims as I've found myself a bit confused. I've yet to find a thread about this specifically but if there is one I apologize and please link me! For information I have a 1978 xs650E with standard 3.5/19 tires in the front and 4.25 18's in the back. My understanding is this corresponds to 100/90 19 and 110/90 18. They also both need replacement. Onto the Question.

So I'd essentially like to have the same size front and back rims, lowering the front to an 18 inch rim. While simultaneously putting in dual disc brakes in the front. Purely speculating I'd like to run 100/90 18's and stick with 110/90 18's in the back. My understanding is this would drop the front a little, & lower the bike.

Will this be terribly difficult to do? Also will it hurt my handling, or rather what tire setup will give me optimal handling. I will frankly stick to the stock tire sizes if this is a difficult task, but part of my does want the front to be a little lower for "The look" or better handling. Other things I have read about when doing things like this is do I have to worry about the shocks/forks.

Please be blunt, if this is a waste of time I believe I'll just stick with what I've got and go for those dual disc brakes & swap my tires out. I'll do my best to answer questions but I don't currently have my bike, getting tabs welded on so I can mount my seat from Westonboege! Also going to bed but will reply as soon as possible. Thanks.

 

[fredintoon]

Hi Vizzinzin,
dunno if re-lacing your front with an 18" rim would be a waste of time or not. I wouldn't bother but I won't make that decision for you.
You could perhaps consider re-lacing to wider rims though, there's list consensus that modern tires are happier on wider rims.
Dual Disks though, BTDT.
Going dual along with stainless lines really does improve the front brake performance.
In a large part because the oversized stock front master cylinder works far nicer when it's working two calipers instead of just one.
But Oh! The extra unsprung weight you get by doubling up on those massive front disks (even if you drill them full of holes like you should anyway) and the worsened handling which follows!
The handling downgrade don't bother my sidecar rig and I ride like a timid old man (and at my age, that's appropriate) on a solo but
most likely your more spirited riding style will be adversely affected by the dual disks' additional unsprung weight.
What I'd suggest you do instead of going dual disk is fit a smaller (11 or 12mm piston diameter) aftermarket master cylinder, drill the disk full of holes and upgrade to stainless brake lines.
Handling will improve if you upgrade to a better class of rear shocks, re-bush the swingarm if it still has the stock plastic bushings and add a fork brace, (I like TKATs but there are others) especially if your search for style involves removing the stock front fender/fork brace combo.

 

[Vizzinzin]

Fredintoon,

Thank you for the answer! I'm frankly kind of thinking it would just suck up a lot of time for little gain on the front tire. Perhaps just putting back the stock sized tires. That's also about my understanding on the brakes, I found a lot more info about that on the way to work. I'm likely going to replace the whole setup on the brakes so I would pickup one of the discs from mikes & the 11mm master cylinder. I think if I had more of a shop to work with & the knowledge I'd be more willing to try some of the less bolt on friendly options but you sound pretty spot on about the heavier front end.

This may be a silly question but with wider rims would I be running fatter tires? My understanding has been the fatter tires give worse handling, and while it is more of the look I don't really want to sacrifice the handling. Rather would I be able to use a wider rim and still fit a 100/90 19 in the front and similarly a 110/90 18 in the back assuming I stick with the stock tires? I saw a thread that made it sound like it would fit fine but I'm uncertain.

http://www.xs650.com/threads/tire-rim-fitment-load-rating-speed-rating-charts.44471/

This was what I read.
Thank you!

 

[5twins]

It seems tire to rim size recommendations have changed a bit over the years. Those charts Gary posted up make it seem like the 650 is on the borderline of being wrong. I think it's just fine. At the time it was built, the thinking on rim and tire sizes was probably a little different. I'm sure it fit the "requirements" of the time. I run the 100 front and 110 rear on stock sized rims, on a '78 Standard too. Like I said, I think it's fine. I don't like a larger 120 rear on there. The bike came to me with one and switching to a proper 110 once I wore it out was a nice improvement. The 120 slowed down steering and handling. The bike was less "flickable" through corners.

I agree, a single disc, well set up, is all these bikes need. I haven't changed my MC but have drilled the stock disc and added the stainless line. I think the brake works very well. I have had to panic stop with it and I had that front tire howling. What more could I ask? That's right at the edge of losing grip and skidding. And that's the most, best stopping power you can get. Once you skid, you're screwed, lol.

I also agree the 18" front probably isn't worth the time and money for the return you will get. I doubt the difference is much, certainly not "night and day". If you want to lower your front end a bit, you can simply slide the fork tubes up in the triple trees a little. But, you can't go much, maybe 3/8" at most, or you run the risk of the fork lowers hitting the bottom tree at full fork compression. I have mine dropped about 1/4". I can't say I notice much, if any, difference, but it's supposed to improve things and it was free & easy. Lowering the front is supposed to more firmly plant the front wheel and give better steering input .....

The 650 is what it is, a mainstream '70s road bike. It was never the top of the line model (well, maybe in 1970) so didn't get what was considered the cutting edge suspension components of the time. Sure, you can make it better than it is, but it's never going to compare to a modern bike. As mentioned, make all the stock setting and components good. Swingarm bushings and steering head bearings usually need upgrading. Rear shocks pretty much always do. Service the forks. Fresh oil makes a big difference if what's in there is really old. Also a bit more oil makes a real improvement. I run about 7 ounces per leg instead of the speced just under 6. Minton modding the damper rods is also a nice pretty much free upgrade.

 

[fredintoon]

Hi Vizzinzin,
I was going to reply but 5twins said it all for me.
FWIW, installing any make of modern street tire will give a better ride than the tires that you are removing did, even when they were new.
Obviously, some modern tires are better than others but I WILL NOT start a tire war, they can get ugly.

 

[Vizzinzin]

That sounds good on the tires, maybe at some point I'll fuss more with the rims but if I can just clean up the ones I have and throw some better tires on that would be great. I also think I've been persuaded on the brakes as well. I think it just looks prettier to have the dual discs and I'd like it to be more effective than it is. There's a LOT of tire posts on the forum as well, I'll do my research and get some ordered up pretty soon here.

I will definitely do the fork adjustment once I get my bike back. Appreciate the picture as well. The Minton mods sound quite interesting. I've read a lot of the forum posts and guides but haven't heard of them yet.... (shame on me...) Probably spent too much time with my face in the carb guide and the service manual. I also definitely don't expect this bike to perform like a modern one, I have definitely enjoyed tinkering with the bike thus far. Since I don't rely on it running all the time I don't really mind having it apart in the garage. Figure I'm gonna hang onto this one for a while and it'll eventually come out pretty!

Again thanks for the posts I'd like to think I've read a lot on here but in two simple posts you guys opened me up to a bunch more crap I gotta do!!

 

[5twins]

This is one of the things I like about this bike. Get it up and running and then you can "ride and wrench" it, doing many of the little upgrades and "fixes" over the next few riding seasons. If you find you really do like the bike and plan to keep it a long time, start watching for a parts bike. They made so many of these, they're not too hard to find. Most of the parts swap between model years so a parts bike can be a little gold mine.

 

[gggGary]

I added some current info, thoughts about my rim/tire mods in that rim thread here.

 

[5twins]

If you're going to try the Minton Mods, you will need a rather small numbered drill bit, a #45, for the top hole mods. This probably isn't something you're going to find hanging on the rack at your local hardware store, and even if you did, it would probably set you back $2 or $3, maybe even more. Being so small, there's a good chance of breaking one if you're not careful. It would be good to have spares. I did an eBay search and ran across a very good deal, a 12 pack for $5. Get your "lifetime supply" here .....

http://www.ebay.com/itm/371545072565