Rear shock options for 250cc

[NewKidOnTheBlock]

Hi All,

I'm finally getting somewhere on my front end conversion/ running gear upgrade on the 250cc cafe racer.

The setup (as I recall, I've been buying these parts over about 3 years)
18” Akront Rims
Avon Road rider tyres
Honda CB?350cc TLS front brake
32mm Marzocchi Forks (from a Montessa I believe, far too long and will need the stanchions shortening)
Yokes/Triple tree from a Benelli, these weren't even a pair and were for the wrong fork diameter but I loved the style so I've machined them to suit
Taper roller conversation to my own design
Stock rear hub

I will need to shorten the front forks and likely change the springs but for now I'm going to drop them through and add spring preload spacers for a trial.

I've been looking for rear shocks now and I note Hagon £150 and Ikon £400 seem to offer 300mm twinshocks marketed for these bikes, nitron and others will also make custom shocks to suit. I vaguely recall speaking to Nigel a long time back and he suggested 310mm I think

What are people's experiences with similar set ups, this is a road bike so I don't want anything too stiff either.

Also, while I'm on the subject, does anyone have some fork length measurements and spring rates for the front if anyone has any ideas where I should be?

Thanks very much!

[Duccout]

What I can tell you is that when it comes to rear shocks, you get what you pay for. Top-quality shocks cost a fortune, but really repay you when it comes to comfort. Cheap shocks deliver sharp jabs to your body, and can be very uncomfortable.

The best value, in my opinion are YSS shocks that are beautifully made and have infinitely adjustable damping, and I speak from experience as I have them on my 1000cc Ducati, and they are fantastic; or even better are Maxton, built specially built for you, but at a price. At the other end, I have NJB shocks on my 250, and for the money, they are pretty good.It all depends how big your wallet is. Many people (including me) think that spending £500 on a pair of shocks for a Ducati Single is not cost effective, but if you can afford it, is definitely worth it.

Colin

[graeme]

I’m going to try YSS RZ362 .
They have good reports and seem good value
I have Koni on my 450. Good shocks but an old design nowadays and the modern Ikon are the same. Not much cheaper than the YSS.
As Colin says, you get what you pay for.
I’ve bought Hagons for a commando and don’t rate them very highly. Again you get what you pay for.

Graeme

[Duccout]

Yes, I must agree with Graeme, I used Hagon shocks for many years, and they are good value, but are low-tech, and give a very rough ride.

Colin

[NewKidOnTheBlock]

2 votes for the yss they look very nice but has anyone heard any users report of good finding with them? I see they are 305-315mm long, I've been looking for anything to corroborate ideal length, one guide in Motoscrubs technical section goes as long as 13" (325mm).

Also does anyone have a good reference for trail distance?

Thank you

[Duccout]

As I said, I've had YSS on my GT1000 since 2009, and they work superbly, have 60 click rebound damping that allows them to be tuned exactly as I like, and they still look new after all this time. The standard length shocks on Ducati Singles is 305mm I believe? (I think that Scramblers are longer) and fitting longer shocks is often beneficial, but can cause problems with chain clearance. If Nigel recommends 310 then that would sound about right.

YSS RZ362 have adjustable damping and they recommend 310mm length, at a price of around £380. There are lower spec ones available without the adjustable damping for around £200.

I must add that the Hagons with adjustable damping (2610?) may be very good, and definitely look to be good value for money, but I have no experience of them, so cannot say how well they work.

Colin

[NewKidOnTheBlock]

Thank you Colin and Graeme for the suggestions, the YSS look pretty appealing.

I've now got both wheels on and used some M12 studding to replicate 310mm shock lengths.

PXL_20210701_190313223~2-02.jpeg

When I measured ground trail I am getting 80mm with this set up, this sounds a bit on the short side compared to the book I've been reading but I'm new to this, does anyone have any idea of what range I should be working to on these bikes?

Overall I'm very happy, it's looking like a proper sized bike now rather than a toy like it did on 16" rims. I do need to do some modifications to my seat bracket mounts at the back to ensure tyre clearance through suspension travel.

[Duccout]

I don't think that trail will be a problem, and I don't recall ever having any head shaking on my Ducati Singles (although that's probably because I'm riding too slowly). BTW, the YSS RZ362 shocks have a length adjuster (possibly 10mm) so there is some leeway with them.

Colin

[LaceyDucati]

80mm trail should be okay, it's only when you go under 75mm things can get a bit lively. In old money between 3 to 4 inchs is usually acceptable, my race bike years ago was about 3.25" (82.5mm) and that was perfect for me. That said although I believe trail is one of the most important factors there are other factors like wieght bias etc that will influence handling. Hope that helps.

Nigel

[NewKidOnTheBlock]

Thanks very much Colin and Nigel.

That's a relief to hear than I should be in the right ball park for trail, this is something I've never really looked into, my dealings with suspension in the past have only really being setting static sag and clicking damper knobs one way or the other! When it comes to messing about with geometry with new yokes, wheel sizes and fork lengths it's really been been an eye opener in how easy it would be to go wrong, luckily it seems lots of early blind guess work hasn't ended up a million miles away.

After tinkering around yesterday some more and finding what clearance I had where I settled on ordering the YSS RZ's from Wemoto, £339 delivered, I'm just a bit gutted that the lead time is 5 weeks though! They told me that the main spring rate is 13kg/mm and the secondary spring is 18kg/mm incase that information helps anyone else out.

I need to get the grinder out on my seat bracket next to ensure clearance but I'm really happy with how this is coming along now. The front end conversion has given me a lot of learning and lots of time on the lathe making stems, bearing cups and the like, it's been far more time consuming than I initially thought and I've made a few mistakes along the way but I'm learning every day.

Thanks all for help along the way.