Talk to me about rear shocks....




greg3852

Registered
So I am looking to do some highway pulls and street racing this summer. I am currently running at stock wheelbase, but hopefully will be going 4 to 6 over. I want the bike to be set up for that. I know I am going to have to change the rear shock, but I know nothing about setting up a bike. I've read the post everyone recommends on here, but I'm still lost. I'm not looking to race any circuits or anything, so I'm guessing I could get away with just replacing the spring? I'm at 220lbs, so I think I'm far beyond the limits of the stock spring nevermind extended.
 

greg3852

Registered
Stock units valving will need altering for a stiffer spring. Budget???
I don't even know what something like this would cost. No idea. I'm looking to still do nitrous, quickshifter, etc so as cheaply as possible. But I do understand I have to pay to play.
 

Mr Brown

Registered
@c10 got his Penske drag shock which I think is a nice option and large range of adjust-ability.

What swing arm are you looking to run? @Mr Brown has a welded and extended arm with underbracing he was willing to sell so you can look into that possibly as well.
I don't even know what something like this would cost. No idea. I'm looking to still do nitrous, quickshifter, etc so as cheaply as possible. But I do understand I have to pay to play.
We can talk about it if you're interested.
 

sixpack577

Top Gun
Registered
At 220lbs, a stock rear shock is ok, extending it 4"-6" is not dramatic.
But, a custom shock will obviously be better.
The fork springs will definately need upgraded at your weight.
As for handling, if the forks are perfect and the rear is not, or vice versa, then the whole ride suffers. Both must be correct.
For suspension sag, it is actually simple.
35-40mm of sag is good for the street, and 30-35mm for a track, as tracks tend to be smooth, and the lower the sag number, the firmer the ride.
That sag reccomendation will have the shock functioning as it should.
Essentially all you're doing is adjusting it to Your weight, and so that the bottom third of the travel is compressed "sagging" under the weight of the bike and rider. That way the middle third of the stroke/travel is where the suspension works. And, the upper third of travel is to be your over-rev, the extra travel needed for bumps or potholes.
Compression is the firmness the shock compresses at. Rebound is how quickly it returns to it's sagged position. And Preload adjusts heigth and a certain amount of "preoaded" tension.
Shooting for set sag numbers is only 3 seperate adjustments. Each done seperately, so you can feel what you changed.
Basically, with the bike upright(have someone hold it for the rear), you want to hold the brake and push down on the forks and rear seat as hard and fast as you can.
You want the shocks to compress and rebound back as quickly and smoothly as possible, without being too soft, or too firm.
Correct sag numbers gets you close, then it's ride, stop, turn a half click, ride, adjust, etc.
Even just wanting straight line performance, sag is important. As it keeps the tires planted for traction and handling, both of which are very important for braking as well.
I am no guru by any means, but am good at making my bikes, and others bikes handle much better.
I always get a kick out of making a few small adjustments to someone's bike, only for them to be amazed, that just a few clicks made a night and day difference.
Still don't quite understand? Don't worry about it. I assure you that the lightbulb will come on, and when it does, it's going to take your riding to another level.
 

busakiller

Registered
Buy a gen 2 busa shock. The gen 2 has a stiffer spring and you need a stiffer spring for a longer swingarm. I have seen a lot of guys go fast at the drag strip with that shock.

With your bike I would go 18 front sprocket and stock rear. Run a shinko hook up rear tire and strap the front. You should be able to do 1st gear rolls with no wheelies or spinning. That's what I run on my bike.
 

greg3852

Registered
Buy a gen 2 busa shock. The gen 2 has a stiffer spring and you need a stiffer spring for a longer swingarm. I have seen a lot of guys go fast at the drag strip with that shock.

With your bike I would go 18 front sprocket and stock rear. Run a shinko hook up rear tire and strap the front. You should be able to do 1st gear rolls with no wheelies or spinning. That's what I run on my bike.
I will be running the 18 front with either a 40 or 43 depending on what it likes.
 

mabupa

Registered
Just got me a Gen 2 rear shock coming in. See how it helps. Thanks guys
Should be a big difference. Your gen1 shock has a 13.1kg spring and the gen2 has a 14.5kg spring. We weight about the same and racetech recommends a 14.6kg spring, so you’ll be pretty much on the money as far as spring goes. How the longer swing arm will affect that, I’m not sure, but you are not doing a crazy long stretch.
 

jeffgordons24

Registered
I’ve heard it is direct swap and the gen2 Is supposed to be 1/2in longer.
Thanks Miguel, anyone running the Progressive Suspension 465-1172B?
They claim to be US made and have 5 position rebound adjustment. I just don’t want to bottom out that is my main concern. My bike was about a month old when I lowered it on 3 position links, lowest setting and first time out.....well I ripped off my undertail lol. And that was just me on it and I was much lighter then..
 



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