Rear coil over spring rating queery

Hi, British newb here & newb to trikes. 1st post & need some advice.

My (yet to be ridden) trike is a Yammy Vmax 1200 (1998) with home built soft tail swing arm & english rear axel (ford escort mk1), compomotive 15" rim wheels. Bike section is stock Vmax as far as I can tell.

It had problems with the rear home built swing arm & shock absorbers when I bought it. I've done a lot to sort that out.

It had the original 1998 stock rear shocks on & they were spent & I've replaced them with some YSS eco lines but the springs seem a little soft. I have yet to ride this - still putting it back together.

I have checked the YSS spec's & their Vmax replacement coil over shocks progressive spring rating is 25-35 N/mm & mine have 20-30s. I know I should have checked 1st but that's hindsight (& ADHD).

My question is, in general, should I be going for the same spring rating as the original donor bike or something a bit beefier?

Previous set up (shocks removed).

[ATTACH=CONFIG]109323[/ATTACH]

New.

[ATTACH=CONFIG]109321[/ATTACH][ATTACH=CONFIG]109322[/ATTACH]

[QUOTE=J-max;897562]Hi, British newb here & newb to trikes. 1st post & need some advice.

My (yet to be ridden) trike is a Yammy Vmax 1200 (1998) with home built soft tail swing arm & english rear axel (ford escort mk1), compomotive 15" rim wheels. Bike section is stock Vmax as far as I can tell.

It had problems with the rear home built swing arm & shock absorbers when I bought it. I've done a lot to sort that out.

It had the original 1998 stock rear shocks on & they were spent & I've replaced them with some YSS eco lines but the springs seem a little soft. I have yet to ride this - still putting it back together.

I have checked the YSS spec's & their Vmax replacement coil over shocks progressive spring rating is 25-35 N/mm & mine have 20-30s. I know I should have checked 1st but that's hindsight (& ADHD).

My question is, in general, should I be going for the same spring rating as the original donor bike or something a bit beefier?

Previous set up (shocks removed).

[ATTACH=CONFIG]109323[/ATTACH]

New.

[ATTACH=CONFIG]109321[/ATTACH][ATTACH=CONFIG]109322[/ATTACH][/QUOTE]

Jim.....Welcome To Trike-Talk.....:wave4:....

Welcome to Trike Talk Jim!!! Since you already have those I would give them a try.With that setup you might be surprised.

Update:

I've managed to get 20ish miles riding in OK then another 40ish not OK (fuel pump + carb issues). To get anything like a decent ride I'm on 42psi in the front tyre (max stated on the tyre) 21psi rears & nearly all the adjustment taken up on the rr springs. There's maybe 20mm left. I don't know if I can get anything nicer, ride wise, with this set up (as I've never ridden a trike before) but it feels OK & stable. This will do for now I think but I will get the next rating up (25-35) sometime in not too distant future.

As an aside I found picture of how far out the original rt rear shock mounting point was when I bought it. This pic has the new YSS shock mounted to the frame & lightly tightened. It's 1" out.

just an observation.. thinking of the weight of rear end vs motorcycle rear frame and rider weight.... thinking tail could be wagging the dog when hitting large bumps on the road so, considering the shocks/springs setup. I would add some structure/weight ( storage/trunk/tool box? to the rear of m/c frame, keeping it as low as possible. us this structure to make adjustable mountings angle/height etc for your suspension...just something to consider. Looks to be a wild ride!

[QUOTE=LarryA;900373]just an observation.. thinking of the weight of rear end vs motorcycle rear frame and rider weight.... thinking tail could be wagging the dog when hitting large bumps on the road [/QUOTE]

From the little I've managed to ride this, that makes sense. It bucks about at the front quite a bit on the crappy pot-holed roads round here. The rear springs are a little soft for this I think &winding them pretty tight has helped. I'll be getting stiffer ones. Maxing out the front tyre to 42psi was also a big improvement. Having 5" of trail at the front kept me very stable in a straight line, reduced the head shake but corners & roundabouts are hard work. I want to cut that trail down & get some steering but this will make it more twitchy. I'll also be fitting a steering damper.

Your suggestion to add rear weight sounds good advice. I want to fit a bigger fuel tank at the rear of the m/c frame, if I were to do that from an old propane bottle that would add a good chunk of metal in the right area.

That's a full width MK1 Ford Escort English axel so it's about 5'6" overall. Nice 'n stable, feels good.

Thanks for your observations, they're helpful. (sorry for the delay in reply).

[QUOTE=J-max;901534]From the little I've managed to ride this, that makes sense. It bucks about at the front quite a bit on the crappy pot-holed roads round here. The rear springs are a little soft for this I think &winding them pretty tight has helped. I'll be getting stiffer ones. Maxing out the front tyre to 42psi was also a big improvement. Having 5" of trail at the front kept me very stable in a straight line, reduced the head shake but corners & roundabouts are hard work. I want to cut that trail down & get some steering but this will make it more twitchy. I'll also be fitting a steering damper.

Your suggestion to add rear weight sounds good advice. I want to fit a bigger fuel tank at the rear of the m/c frame, if I were to do that from an old propane bottle that would add a good chunk of metal in the right area.

That's a full width MK1 Ford Escort English axel so it's about 5'6" overall. Nice 'n stable, feels good.

Thanks for your observations, they're helpful. (sorry for the delay in reply).[/QUOTE]

once u get the trail reduced.... most likely will not need a damper