Topic: Fitted shorter Rear Shocks & Beefed up front springs - ride now harsh

[nancy]

I removed the stock rear shocks which seems to be 13.25" and fitted another set of originals that the PO gave me with the bike. These are shorter at 12.75". They ride firmer with a bit less bounce over humps etc, but I wondered if it would be best to make a compensating front fork height adjustment? It's riding OK with it's arse a bit lower so I've made no changes to the front - except to remove the springs and decided to top them up with 15mm of spacers - they measured 500mm and 505mm. That had given a ride I'd descibe as harder and more work through the arms with vibration. That has me wondering if stiffer springs normally deliver this - as I've always ridden this bike with the soft front - or, maybe the front should come down at the forks by 1/2"?? My gut feeling is to pull out the front spring spacers - drop them down to say 10mm. I did this change in 2 stages - I put in spacers of about 6mm to start and the ride was not noticeably different. So stepped up to 15mm.
What effect on the ride does the fork oil have? Apart from lubing the insides - I gather it is compressed by the piston to provide downward damping? I replaced this oil last month and used auto trans fluid. Is it worthy replacing with motorcycle rated fork oil. I have since bought some - 10w grade.
Any ideas?

[Inigo Montoya]

Stiffer springs increase the rebound thus making the ride harsher unless additional dampening is added. However additional dampening can slow down over all shock action and make the ride mushy and slow to respond.
Any particular reason you added the spacers in the forks? I would just take them out unless you really needed them for some reason.

[MCRider]

What bike? Assuming CB750, you should not have to adjust the front end as the stock shocks from Honda were 13" IIRC. So you're really not down but a .25". OCICBW

Putting spacers in the front is going the wrong way if you want a softer ride. If your fork springs vary by 5mm they must be sacked and anything you do will be a compromise. Stock shocks and springs are really only good for about 10K if that, less with a fairing or 2 up. So don't resist buying new.

[Jerry Rxman Griffin aka MuthaF'er]

Fork oil weights does make a difference. Reset the rear shock preload and see what that does.

[Bodi]

Stock front forks have basically no compression damping and rebound damping is controlled by wear and oil viscosity. Too thick oil will make the front end pump down over bumps, eventually bottoming out on a washboard surface. The difference in compression damping - ie feeling stuff like expansion joints - is slight.
Too thin oil and the front end will pogo up and down a bit.
Oil volume does a difference because the air above the oil acts as a spring when the fork is compressed - the air is also compressed, pushing back outward. More oil increases the airspring effect, but too much fluid will pop the seal out on a big bump because the internal pressure gets too high... especially if you have so much oil there's no airspace left at or before full fork compression.

[nancy]

Thanks for responses guys. Yes it's CB750 - damn, thought I had that in  my sign. I'll alter that. I fitted the spacers as an article by HONDAMAN recommends doing so to springs that have mellowed with age. His advice was to add "at least between 1/2 and 3/4".
I'm not trying to soften the ride. I noted that the front forks were soft. I could pump the bike front up and down and noted 2-3 inches of travel up front. If I rode (as I do often here) over country roads, front wheel did alot of up and down. So I read up on FAQ and noted HONDAMAN article on packing up the springs to improve ride.
I agree that new springs are the real deal here. But money is limited. Have just fitted new tyres last week. That helped. Rear socks next. Front springs maybe after that.