Is 120/90-18 rear tire to big?

[a40nabowl]

Hi. So I just got my first xs400 and i am not sure what is the biggest tire that you can slap on the rear. It has a 120/90-18 and the chain is touching the tire and the chain has 0 play. My first guess was that the guy who sold it to me just slapped everything together before I came down. So is the 120 tire to wide or is it more likely the tire is not aligned ?

 

[HoughMade]

I have heard of other running 120s and possibly 130s without the chain touching the tire. Your wheels are not stock, so my money is on a spacer issue.

 

[a40nabowl]

I have heard of other running 120s and possibly 130s without the chain touching the tire. Your wheels are not stock, so my money is on a spacer issue.

I was thinking or hoping it is just bad alignment cus the chain has 0 play and it looks like the guy just putt it together before he sold it.

 

[XSLeo]

You can try properly adjusting the wheel for alingment and chain tension. It might help. Another thing is the rear sprocket, is it aligned straight with the front? If the rear is off toward the wheel, the chain will rub.
As you adjust the wheel check the distance from the center of the swing arm pivot bolt to the center of the axle. get them the same, now chak to see if the tire is centered in the swing arm. If not you need to adjust it with spacers.
Once you confirm the wheel is centered check the sprocket alignment. Look from behind the nike at the chain, does it run straight from the rear to the front. Any bending then the rear sprocket needs work. If to far in then a shim between the sprocket and wheel. To far out and you need a dished sproicket made.
Leo

 

[Pork Chop]

What are those wheels off? I think they look cool and a nice big front disc too. Can you post a pic of the other side of the bike so I can see the exhaust.

Cheers.

Posted via Mobile

 

[a40nabowl]

What are those wheels off? I think they look cool and a nice big front disc too. Can you post a pic of the other side of the bike so I can see the exhaust.

Cheers.



The wheels are suzuki GS500 wheels

 

[frwinks]

nice setup and welcome aboard I'm running a 120-90 dual purpose tire on a stock 18"wheel with no rubbing. Previously I ran a 130-90 on a stock 16" rim with no rubbing.
Something tells me that the gs500 rims are wider than stock xs wheels and you're getting da rub. 0 play in the chain is not good either, you should have at least 1.5" of slack in the chain

 

[a40nabowl]

nice setup and welcome aboard I'm running a 120-90 dual purpose tire on a stock 18"wheel with no rubbing. Previously I ran a 130-90 on a stock 16" rim with no rubbing.
Something tells me that the gs500 rims are wider than stock xs wheels and you're getting da rub. 0 play in the chain is not good either, you should have at least 1.5" of slack in the chain

I also am not sure what the swing arm is from. My brakes are welded below the swing arm and do not have the tabs on top like the original swing arms and that is why there is no slack in the chain. I may have to add a few links since there is not much room to move the tire back before it hits the inside of the swing arm. I am also scared of the weld on the brakes. The weld pools do not look even so I question the welders work. That rear end is really a concern. Can anyone guess the swing arm?

 

[frwinks]

can you post a close up of the brake set up? Are you saying that the caliper mounting bracket is welded solid to the swinger? With no back and forth movement to account for varying chain length?

 

[a40nabowl]

can you post a close up of the brake set up? Are you saying that the caliper mounting bracket is welded solid to the swinger? With no back and forth movement to account for varying chain length?

Yes, you are correct and that is why I have to add a few links if I want any slack. This whole back end is really scaring me. I will take the photo of the brake and swing arm when I get home after work and post it. I think adding a few links with correct alignment should do the job. Then I will have someone else weld the brake bracket from the back side as well just to make sure that SOB is on it good.

 

[frwinks]

The PO was a butcher You want the caliper to be "floating" on the arm, you can't mount it solid. As you adjust the chain tension, the caliper has to be able to follow the rotor either back or forth for proper pad/rotor engagement. Easiest way is to mount the caliper to the axle spacer via a bracket. Then either incorporate a brake stay tab or a brake arm into your design to hold the thing from rotating

 

[a40nabowl]

The PO was a butcher You want the caliper to be "floating" on the arm, you can't mount it solid. As you adjust the chain tension, the caliper has to be able to follow the rotor either back or forth for proper pad/rotor engagement. Easiest way is to mount the caliper to the axle spacer via a bracket. Then either incorporate a brake stay tab or a brake arm into your design to hold the thing from rotating

let say my chain had some slack and that was not the issue, and I left the bracket welded to the swing arm. the wheel moving up and down is not an issue from what i can think of since the rotor, wheel and brakes would all be moving up and down together, but why would the rotor move back and forth while riding down the road??? I am just learning all of this so please excuse my ignorance in advance , what are my consequences? Because the last issue I ever want while riding is braking issues

I am contacting the previous owner who did all the work to get some history on the bike and figure out what swing arm this is. The guy I bought it for got it in a trade so he has no idea.

And I have read countless places that adding links to a chain is not a good idea.

Thanks for all your advice btw,

 

[frwinks]

The up and down movement is not the issue, the front to back wheel movement as you adjust the chain is. What the PO did, was locked out the chain and welded the caliper bracket based on that position ONLY. Now if you wanted to slacken the chain, you will not be able to adjust the position of the caliper to the new rotor location. Depending on the angle of the caliper mounting, you might not even be able to slacken the chain at all... It's hard to say without seeing things.
take a close up pic of the pic, we'll see how much adjustment you can squeeze out of the current set up, might not have to add any links at all, just loosen things up a bit


I suck and explaining things, so here's a visual

The long slot in the mounting bracket allows the caliper to "float" back and forth with the wheel as you adjust the chain length therefore changing the position of the caliper in relation to the rotor... clear as mud?

 

[a40nabowl]

You can see the chain touching but there is 0 play in the chain on the top but on the bottom chain I can push it up 1 inch.

Do the swing arm look like what belongs on this bike?

 

[frwinks]

The swinger looks like a stock unit...
here is a good "how to" on adjusting chain slack and rear wheel alignment. It also shows one of the proper methods of attaching a rear disc brake.

You can adjust the existing chain ( slide the wheel forward) and prolly don't have to buy a new one ( once you have some slack in it, and follow the instructions in the vid, you can determine if a new chain is needed or not).
The bad news, the caliper bracket/caliper will not allow you to slide the wheel forward much if any at all ( I circled one of the problem spots in the attached pic). As you slide the wheel forward, the rotor will bottom out on the caliper.

 

[HoughMade]

The swingarm is stock for a drum XS400. Here is the swingarm on a stock disk bike...mine. If you can't quite see it, there is a bracket that locates the caliper to the axle so that the caliper maintains the same relationship to the axle no matter where the axle is adjusted. There is a rod that runs from the caliper to the forward portion if the swingarm that keeps the caliper from spinning.

 

[a40nabowl]

WOW, Thanks so much man. Words can not describe my appreciation. I will make sure to return the advice in the future to someone else in need of help, that is once I learn a bit more my self..

Here is a photo of my current slack .. I overlapped the 2 photos as best as i could..

 

[a40nabowl]

Thanks for the photo. I think the reason they moved mine to the bottom is since the wheel is wide and there is no room with the Suzuki wheel by the axle for the stock caliper.

I will give it a go in the morning with the Video that frwinks sent me and see if I can fix the tire rubbing issue after an alignment attempt.

 

[frwinks]

I'd give it another .5" or so.. I like to run mine on the loose side rather than too tight.

 

[Woody101088]

so do you still have this bike? do the GS500 wheels work well?