rob_zxc

Hi folks

I'm considering buying a mountain bike for fitness / losing weight issues. Perhaps a used Santa Cruz from ebay.

I need advise on the adjustment and settings of rear suspension systems. As I'm a fat sod at 18 stone (250 pounds) will the shocker be maxed out at full travel simply by me sitting on the bike? What's the maximum weight that can be handled?

Also I'm a bit confused with tyre and rim sizing. I've googled for thornproof tyres:

Schwalbe Marathon XR 700 x 50C, 50-622.
05 Team Control Armadillo Tire Size: 26 x 2.00

so do I buy rims to suit tyres instead of tyres to suit rims? Or is there a slight range of rim widths that a particular tyre can fit?

TIA
Rob

Speedub.Nate

What model? You're too heavy for a Superlight, but no problem for a Heckler. I'd be cautious about a Blur as I think you'll be near max PSI.

Maelstrom 

First upgrade would be a suitable spring. But really here is the info you need to find

i2i of the shock
stroke of the shock

When you find this information out you can then calculate leverage ratio of the bike. Esentially finding out how much stroke is used for 1 in of wheel travel.

6" wheel travel
2" stroke shock
equals 3" of wheel travel to 1" stroke of shock. a ratio of 3:1.

So a basic calculation to us to find out approx what spring rate you need is to multiply your weight * the ratio (so 3 in this case) You would need a 750pound spring.

Without knowing if the suspension design is a rising or falling weight or other factors this is about as accurate as you can get. If the bike has a crappy leverage ratio of say 4:1 you would not want to use this.

a) the spring would need to be soooo stiff you likely couldn't find one
b) you would blow through the shock like butta and likely destroy it. Shocks aren't really built to take 4:1 ratio. (well maybe the avy I guess) 3:1 is ideal.

Gets technical but especially at a heavier weight you have to understand this concept when buying full suspension bikes.

cryptid01

Welcome.
Most of us who are near your weight prefer a coil shock rather than an air shock, as we have to run near the maximum air pressure of the shock, which can sometimes lead to premature seal failure. This is not an issue with a coil spring. But as Maelstrom indicated, the correct spring rate is critical for performance, and the lower the leverage ratio, the better the quality and tunability (is that a word?) of the shock damping.



You will need to narrow your search to 26" tires exclusively if they're going on a mountain bike. There are measures you can take to fight flats even without a "thornproof" tire - put self-sealing Slime in your tubes, use strips (Mr. Tuffy used to make some at one time) or you could even look into tubeless tires. Unless you're riding in an area with lots of cacti or similar spiny vegetation, punctures may not be a major issue.

Make sure to post pictures of your bike when you get it built up.

rob_zxc

Thanks for that fellas.

It seems I've got a fair bit of studying to do!

Killer B

Simply running higher air pressure will eliminate 75% of all flats. Try 45-50 lbs. F&R, that's what I run. As for the bike, I'd opt for a more "beefy" frame type. Santa Cruz bikes are lite for a reason, they're simply not beefy framed, therefore they're more likely to break or crack at some of the high stress points, especially by heavier & more aggressive riders.

cryptid01

Well since he's just getting into mountain biking for fitness and weight loss, I think it will be a while before he's considered "aggresive" or too much for a SC.

Killer B

I guy I know weighs 220 & he's broken the frame on his Blur twice. He's thinking of selling it because if he breaks it again, maybe they won't warranty it.... He doesn't jump it, just too heavy for the frame design I suppose.

Raiyn

If this is your first MTB skip the full suspension and get a hardtail. No rear suspension means no shock issues. Also newbies really shouldn't purchase bikes online. It's really easy to get screwed if you don't know what you're looking at. There's also fit issues involved. Your best bet will be to go to a local bike shop (LBS) that will assist you further