Calculating Correct Spring Rate

[Corky78]

All,

I need to change my rear shock lower bearing (which I have purchased but need to fit). While doing so, I want to upgrade my rear spring as it's clearly too soft for my large frame (thought about losing weight, but buying a new spring is easier!!! ).

Looks like I have an 80Nm spring on at the moment.

I've read (probably too much) varying reports on what you need to do, what spring is best, progressive and set spring etc and don't know what to believe. Others say it's all down to the sag setting etc. What advise do we have on here? Anyone done it? Anyone found a reliable calculator that you put your weight into and it gives optimum settings etc?

I've checked what is available for my bike and they go up to 84Nm or 76-95Nm (I guess that's the progressive one). Would I need to upgrade the front fork springs too?

Any help/advice would be appreciated - I'm no expert mechanic, or professional Enduro rider, so just want the right spring to do the job without me having to fiddle every ride

[6daysextreme]

i would defo adjust the sag setting before you do anything else - it makes the world of difference especially on a KTM.
The standard spring takes an awful lot to need to be upgraded and replacing the lower bearing does not involve taking the shock apart.
A good tip is to put the new bearing in the freezer overnight to ensure easier fitment. Its extremely unlikely to need the front springs replaced for your size, its normally for a different rate of suspension. Saying that i have changed both sets of my KTM forks springs.

One of the best things you can spend money (if you have it to burn) on is a suspension specialist set up, cannot recommend it enough

[Billy]

How much do you weigh ? Strongbow used to ride a 450 exc and he is a fat bastard, pm him and see what springs he was using.

[Dave]

Didn't Strong bow ride one of these?

[Corky78]

Well, good & bad news on this.

Took it into P&H Crawley for a "specialist set up" and unfortunately, the shock is cream crackered. My preload on the rear was wound all the way in and was making zero difference to any of the settings. The spring is an 80nM which is designed for riders who weigh between 75 - 85kG. I'm slightly more than that! My front forks needed bleeding. Unsure of what springs are in the front and only have adjustment on the top.

So, after quoting me £650 for a full overhaul, front and rear, including new springs all round, I opted to go for a full refurb on the rear (to get it working properly) and a new fat bastard spring. Then, I'll see how that feels once the sags are set up. Still £300 down but should make a massive difference. I've already done the lower shock bearing myself - took an hour or so.

I've decided to overhaul the fronts (and check if I have the right springs before ordering new ones!) myself so at least I know I have new seals and oil all round and it won't need doing for a while

Should keep me busy over the winter period - hoping to be back out again after Christmas.

[GDAS]

when I bought my EXC-F 350 the previous owner had put uprated Eibach springs in to match his 16st weight. He also gave me the original springs so being a bit lighter I swapped back to standard.
The Eibachs are like this http://www.ebay.co.uk/itm/191008295299 mine have got a spring rate of 0.44 kg/mm
I'm not using them so would happily sell them if you're interested.
Graham