Rear fender wheel clearance..

Hey guys,

I'm trying to figure out how I'm going to put a Brat seat on my XJ650, the way in which the frame dog-legs up at the back and the high amount of fender that comes up makes me question how to get a brat seat done.

I'm trying to make it so I can get a passenger on the back here... but I'm concerned if I just come straight back with the seat from the tank to a frame loop it's going to bump on the rear tyre at full bounce... any experience on this would be appreciated.

 

Can you post a picture of what you have now ?

 

I'll take another pic tonight more close up but here's side view -- just kinda stock...

I'm looking to make it like the back end on this:

http://www.pinterest.com/pin/421860690067471563/

 

Here's a better shot if you can see this on flickr...

https://www.flickr.com/photos/orsburnbo ... 4316451995

The question is how much of the rear fender and internal mudguard can be shaved off and lowered without the wheel hitting it on full bounce.. to me it looks like the blue bike has had this taken off at least down to an inch about the rear frame..

 

measure the length of travel there is on the shocks before the damper rod bottoms out,
then add that length to the top of the tyre. that should give you the amount of clearance you have.
if the shocks are at an angle, as in the picture, then once you have the amount of travel measured, remove the shocks and jack the swinging arm up, until the shocks would have bottomed out.
stu

 

I kinda thought about that logically -- but was wondering if the shocks would ever get to full compression and what kinda clearance is best practice.

 

I don't have your answer, but I do have an alternative suggestion for finding out: take a ratchet strap, loop it through the wheel and over the frame, and crank it down as tight as you can.

 

Good idea -- thanks dude.

 

I did this:

Put the bike on the centrestand.
Measured the distance between the shock mounting centres.
Measured the distance between the damper body top and the rubber bump stop.
Subtracted the second measurement from the first.
Noted the result, which is my suspension travel at the shock absorber.
Took the shocks off and jacked up the swinging arm until the distance between the shock mounting centres equalled the result of my sum above.

The wheel centre is further away from the swing arm pivot than the shock mounting; the wheel suspension travel is greater than the shock travel. Once the above is done, there is no more messing around with rulers and although it takes a little while, it saves time later on.

I was doing this to allow me to install a cross brace for my home made pannier fixings. It fitted above and behind the tyre. I allowed an inch clearance, to be sure.

By the time my wheel is at the top of its travel it is starting to move away from the cross brace, so that worked well. However, it would be a good idea in your case to take some account of the compression of the bump stop; allowing perhaps 10mm compression to produce a result 10mm shorter than the one I found, above. So the tyre would end up perhaps 11 or 12mm higher.

How much clearance you add to this is up to you, but remember that different maker's tyres may have slightly different dimensions for the same nominal size. Don't forget about bolt heads sticking out.

Another thing to think about, is how comfortable do you want your passenger to be? If the passenger is to be your 'other half' that's one thing. If it's the occasional friend you might not care so much.

 

I did this:

Put the bike on the centrestand.
Measured the distance between the shock mounting centres.
Measured the distance between the damper body top and the rubber bump stop.
Subtracted the second measurement from the first.
Noted the result, which is my suspension travel at the shock absorber.
Took the shocks off and jacked up the swinging arm until the distance between the shock mounting centres equalled the result of my sum above.

The wheel centre is further away from the swing arm pivot than the shock mounting; the wheel suspension travel is greater than the shock travel. Once the above is done, there is no more messing around with rulers and although it takes a little while, it saves time later on.

I was doing this to allow me to install a cross brace for my home made pannier fixings. It fitted above and behind the tyre. I allowed an inch clearance, to be sure.

By the time my wheel is at the top of its travel it is starting to move away from the cross brace, so that worked well. However, it would be a good idea in your case to take some account of the compression of the bump stop; allowing perhaps 10mm compression to produce a result 10mm shorter than the one I found, above. So the tyre would end up perhaps 11 or 12mm higher.

How much clearance you add to this is up to you, but remember that different maker's tyres may have slightly different dimensions for the same nominal size. Don't forget about bolt heads sticking out.

Another thing to think about, is how comfortable do you want your passenger to be? If the passenger is to be your 'other half' that's one thing. If it's the occasional friend you might not care so much.

 

I took more of a "f***-it just wing the shit out if it" approach and can confirm the clearance is about 4 fingers... that's man hand fingers... hey I'm a professional... with a generous portion of erring on the side of caution I think I can put a small fender that arch's upto the top, level with the frame tube