Lowering rear suspension

[aliissari]

I'd like to know how much anyone has lowered the rear suspension on their XS650 using shorter shocks.

I have an '82 XS650 with aftermarket 11" Hagon shocks and a stock 16" wheel with a MT90 (130/90) AVON Safety Mileage MK II tire in the rear.

I expected to still have enough clearance between the rear tire and frame since the new setup is only 1.5" shorter but it's not working out - see pics.

So what I have on the bike now is:
280mm / 11.0" at 8.6" fully compressed and with 2.4" of travel

Two other options from Hagon I'm considering are:
310mm / 12.2" at 9.0" fully compressed and with 3.2" of travel
300mm / 11.8" at 8.6" fully compressed and with 3.2" of travel

I've also lowered the front by 2" using HHB lowering kit but I think I'll need to adjust the front by 1" when I swap the rear shocks.

Any advice would be appreciated, and thanks in advance.

 

[CoconutPete]

Wait - you are thinking about going lower than what you show in you pictures? Am I reading this wrong? You don't look to have much space to play with.

 

[aliissari]

@CoconutPete No, what you're seeing in the pics are the 11" shocks, which at 1.5" lower than stock are too low.

 

[CoconutPete]

Now I understand, sorry.

I have seen bikes with shocks as low as 10" but with your shortened frame and your flat seat pan that's going to change things dramatically. I'll let someone else chime in on that one :-D

 

[aliissari]

@CoconutPete the seat pan may be flat but the frame isn't shortened... Unless you mean the Heritage has a shorter frame?

I've seen 10" shocks as well. And with fat tires like mine. I just can't figure it out - the math isn't adding up.

Attached is the only picture I have of how the bike looked when I purchased it from the PO (it's a screen shot from a video). It has what I believe are the 12.5" stock shocks and a Shinko 240 tire in MT90 (130/90), and although the suspension looks a little lower than stock there was enough clearance.

Also attached is a wider pic of the current setup, 11" Hagon shocks and a AVON Safety Mileage MK II MT90 (130/90), which has almost no clearance.

 

[fredintoon]

Hi aliissari,
Like you say, if you lower the bike's arse end that far the tire will rub.
And if you re-lace the rear wheel hub into a 14" or 15" rim to get tire clearance the bike won't sit level.
Your build looks to be a street racer? I'd say leave the front where it is and fit 13" rear shocks to lift the
bike's arse and quicken it's steering.

 

[aliissari]

@fredintoon thank you for the suggestion. It's not meant to be a street racer, however. It's only meant to get my feet flat on the ground. Do you think a smaller tire, say a 4.60, would be the best route? There aren't many tire options in 4.60 that I like and because it's not the stock size tire I killed the idea early on, but if I'll reconsider it if there's no other way.

The "performance" mods I've made so far are:

-PAMCO complete high output ignition and advance
-HHB PMA system
-Sparx capacitor (running the bike w/o a battery)
-starter block off kit
-UNI pods
-650 Central premium BS34 jet kit
-All Balls tapered roller bearings
-bronze swingarm bushings
-Joe Wiseguy swingarm brace
-HHB lowering kit (using the 2" kit at the moment but also have the 1" kit)
-Race Tech straight springs
-Hagon 11" twin shocks
-Vesrah brake pads

I'd like to eventually change the sprockets and upgrade the carbs and exhaust but am in no rush to get to those mods as the bike runs pretty well right now.

And here are the "performance" mods the PO made (I have receipts/records to back up most of this):

-top end rebuilt at 15k original milage and have put ~2k on it since.
-full top end rebuild (to update cam chain + guide) done personally with receipts for all mikesXS replacement parts. Cylinders honed, valves & seats cut to spec by machine shop
-carbs are jetted perfectly for the shorter exhaust and pod filters
-clutch was rebuilt less than 200 miles ago - trans is bulletproof and shifts through all gears like butter
-HHB master cylinder w/ stainless steel braided line
-MikesXS brake caliper
-XSperformance cross drilled brake rotor
-custom front fork brace

 

[xjwmx]

The first picture looks like stock shocks turned 180 judging by the little hole on its cover. Smaller wheels on front and back or maybe thinner tires, with as short of shocks as the arrangement will stand is all that comes to mind. Technically it's ok to just be able to reach the ground with your toes, but I wouldn't like that at all myself.

 

[aliissari]

@xjwmx thank you for the wheels/tires suggestion. I've considered a 19" front and 18" rear set up with thinner tires, but based on my research the diameter of a 18" wheel is 1" taller than the diameter of a 16" wheel. (I don't love the idea of a thinner tire on a 16" wheel.)

 

[fredintoon]

Hi aliissari,
that's quite a list of upgrades you posted.
I'm in agreement with some of them and against others but that's a different discussion.
But that ain't any help in getting your feet on the ground at stop lights.
Options:-
Bratstyle-copy frame mod to lower the seat height. (not cheap to do and perhaps not a look you'd like)
Platform riding boots. ( If folks only see one boot at a time they'll respect you for riding with a disability)
Get used to stopping on your tippytoes (the only free fix)
Hang a sidecar on it (a left field option, I know, but a sidecar is a great chick magnet)
However, a 4"-18 tire has eff nigh the same outside diameter as a 5"-16 tire
25.2" vs 25.0" (OK it has a 1/10" bigger radius) but it's 1" narrower so it may
fit more into the middle of the bike's rear fender to give a little more clearance.

 

[aliissari]

@fredintoon thanks for the suggestions. I ordered a 4.60 tire and will see how that works, but my gut says I won't like it. And I don't think I'll go down to 4.00 on a 16" wheel.

 

[jamesgs4]

either change your seat, or get longer shocks.

 

[fredintoon]

@fredintoon thanks for the suggestions. I ordered a 4.60 tire and will see how that works, but my gut says I won't like it. And I don't think I'll go down to 4.00 on a 16" wheel.

Hi aliissari,
um, where do you get inch-size tires (you quote 4.00-16 & 4.60-16) these days?
All I can find is metric/inch sized tires. For instance the original Special rear tire was 5"-16 but the book now says 130/90-16.
And it's the number after the slash that should interest you.
xx/90 means that the tire's height is 90% of it's width. But 90 ain't the only %age they come in. Try for a 125/75-16?

 

[aliissari]

@fredintoon the AVON Saftey Mileage tires and IRC GS-11 tires (vintage style tires) list their sizes in inches. I guess it's a nod to the vintage style?

I think a 125/75 would be around 3.7", and although that would get me closer to the ground I feel like it would be cutting off my nose to spite my face :/

That said, i'll research it further. As always, thanks for the suggestion.

 

[FLEA]

tried 11inch rebel shocks on a stock bike , there was no rubbing and I got a 15 stone mate to jump up and down on the seat ,with a couple of fingers inbetween tire and guard , barely touched my fingers , now the bad part , was like riding a hard tail , switched back after 2 weeks , was killing the kidneys (my guess was something to do with the angle of the shock on xs compared to the angle on the rebel)

 

[gggGary]

tried 11inch rebel shocks on a stock bike , there was no rubbing and I got a 15 stone mate to jump up and down on the seat ,with a couple of fingers inbetween tire and guard , barely touched my fingers , now the bad part , was like riding a hard tail , switched back after 2 weeks , was killing the kidneys (my guess was something to do with the angle of the shock on xs compared to the angle on the rebel)

Did the same thing, one trip to town cured me of THAT idea. Was like the 4th of July, showers of sparks, dragging parts on every corner. Yuck!
How about lengthening the swing arm? Looks like you could get that seat lowered an inch to the frame......

 

[aliissari]

@gggGary lengthening the swing arm is an excellent idea! BUT I've already welded the swing arm brace in place so would need to start over with that. Not opposed to doing that, though. And you're right about the seat. I'll look into that. Thank you for the suggestions!

 

[fredintoon]

@fredintoon the AVON Saftey Mileage tires and IRC GS-11 tires (vintage style tires) list their sizes in inches. I guess it's a nod to the vintage style?
I think a 125/75 would be around 3.7", and although that would get me closer to the ground I feel like it would be cutting off my nose to spite my face :/
That said, i'll research it further. As always, thanks for the suggestion.

Hi aliissari,
tires that look "vintage" are only OK if they are moulded out of modern rubber. but you already know that, eh?
And before you sink more money into different sized tires have you road-tested the tire that's on the bike to see if it clears or not or are you just guessing?

 

[CoconutPete]

I guess it doesn't look as odd as I had first thought. My shocks are 13 3/16" and I guess I have about 2" more than you.

 

[aliissari]

@fredintoon yes, all of the tires have modern compounds - the vintage style is more of a look than anything.

No, I haven't road tested the AVON tires and 11" shocks but not because of the costs of the tire, because of the cost of the shocks. That said, I'm confident the tire doesn't have enough clearance.

But before I swap the 11" shocks for 12" or 12.2" I'm going try different 130/90 tires.

@CoconutPete thanks for the reference. Also, what size tire do you have?