I am around 260lbs and I have a stock rear shock on my DR650. Is it necessary to change out the entire assembly? Or, can I just replace the stock spring with a heavy duty spring?

Hi

You will be able to change the spring.

If it's a very old, beat up shock then a whole new unit of better quality/technology would be a nice upgrade.

Depends on the depth of your wallet.

__________________
Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

Spring.

At a first order level;

The spring is used for the weight of the vehicle + load.

The shock (damping) is for the unsprung mass (wheel, tire etc).

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A good spring provider given the bike model/year, your weight and the weight of any luggage will be able to specify what spring rate (amount of compression for a given load) you need, and will then provide a spring that is closest to the required rate.

Again this will depend on the depth of your wallet - buying a 'heavy duty spring' will be cheaper than going to a place with specialist knowledge. But you may have to buy several springs to get it right yourself.

Some very rough calculations as a sample?
Rough % - change to suit the bike
60% of the weight of the bike is on the rear wheel
70% of the riders weight is on the rear wheel
130% of the luggage weight is on the rear wheel

Standard bike cal would be something like
60% of 500 pound = 300
70% of 160 = 112

total 'standard' weight on rear wheel =412

Your bike cal would be something like
60% of 500 pound = 300
70% of 260 = 182
130% of 20 = 26

your total weight on rear wheel= 508

rate change = 508/412 = 1.23

So take the standard spring, measure its rate and multiply by 1.23 for your 'ideal' spring rate.

Change weights to suit what you have, change % (percentages) to suit the bikes geometry.

You will end up at a 7.8, 8.1 or an 8.4 rear spring, depending on your riding style, load and use. You don't have to upgrade the shock, but it makes the DR a damn site better if you do - and don't forget to stiffen up the front end on the DR to match and use some drop in valves, I did a write up on them here:

http://www.horizonsunlimited.com/hub...ed-you-50952-2

depending on which valve type you use, you will need differing spring rates for the front end, Cogent Dynamics do IMO the best DR suspension, drop Rick a line and ask him what will work, or talk to Procycle who sell Cogent gear.

https://procycle.us/bikepages/dr650.html

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Cheers
Grif

'11 KTM 450 EXC
'09 Suzuki DR650
'00 Discovery Series 2 V8
'95 Defender 90 300 Tdi Overlander
http://gipperstravels.blogspot.ca