Rear Shock Length vs. Front Fork Lowering

[Nits78]

Go easy here ... I'm fairly new to this forum, and I did my best to search high and low for an answer, but there seems to be nothing definitive. So, I guess I'm looking for anybody willing to share their experience.

The Situation:
1975 XS650 cafe build, 34mm front forks, billet aluminum triple tree (flat across), therefore lowering the front forks about 1.00"-1.125" and sharpening the steering. There are no significant changes to the frame, and the bike lost a lot of weight (stock equipment minimized/eliminated/replaced).

The Question:
The rear shocks need replacing, and I plan on going with a set of Ohlins. I know the stock rear shock length should be somewhere in the range of 12.625" or 320mm with about 80mm of stroke.

So, given the front end already went down about an inch, how will the geometry or handling of the bike be affected if the replacements are longer (330mm/13")? Aside from ride height and ground clearance, is there a benefit? I am leaning toward maintaining the stock length, but I have no idea why, I just think it seems right.

I'm about 150 pounds and not the tallest guy in the world. 90% of my riding has been on 600cc sportbikes (Honda CBRs/Yamaha R6s), which is what I'm used to. I'm not trying to achieve that kind of handling ... I just prefer something fun and fairly safe at a moderate to high speed in a turn.

Ohlins Shocks are not cheap so I want to try my best to get this right "enough" the first time.

Nits78

 

[jd750ace]

While the pitch of the frame will be a bit forward, your rake and trail should still be stable, and a bit quicker steering than stock for sure. My big question is, what are you doing to the internals on the 34s to match the big money performance the Ohlins should deliver on the rear? A perfectly set up rear is not much use with a mushy wallowing front.

 

[Nits78]

Good question. Race Tech is transforming our terribly mushy and wallowing front forks into something quite different (new springs, cartridge emulators and oil). I also just got my TKAT front fork brace and new parts for a steering stem bearing job. Don't worry, I won't leave out the swingarm either, but I have no immediate plan to brace it or replace it.

 

[jd750ace]

Good shot on the Race Tech front. My Road Star and Sv650 are both Race Tech fronts. Rear as well on the SV, but with a gixxer 750 Showa shock.

 

[pereiracycles]

Did you ever find a set of Ohlins for your 75 cafe project?
I've got a '75 and would like to fit up some ohlin's but have the same question as you.