Front and Rear Suspension repair/replacement

[Abiram Menon]

Hi, Thanks to the subpar Indian roads, my front and rear suspension are suspected of being gone. There is absolutely no issue on smoother undulations, and the suspension still works, though it rebounds with a sharp jolt on road joints or in poorly built rumble strips. Is it a sign of the early stages of wear? I also heard the rear suspension can't be repaired, but what about the front?

 

[Gary in NJ]

Using Gold Valve Emulators and linear-rate springs the front suspension can be modified to work quite well, with adjustable compression and (limited) rebound damping.

The shock is a different story. It’s a sealed emulsion shock that is not designed for rebuild. I’ve seen one member (who has extraordinary skills) rebuild the shock, but it is quite an undertaking. Wilber, Hogan and Ohlins all make bolt-on shocks.

 

[Abiram Menon]

Thank you, Gary. What about YSS rear shocks? Also, is the R6 suspension the same?

 

[Gary in NJ]

Being a linked design, the R6 is very different. I have not seen a YSS fitment for the FZ6. If you know of one, please provide a link as I'd like to see the specs. As you may know, quality from YSS can be unpredictable.

 

[Abiram Menon]

Hello Gary, Here is the link for the YSS shock absorber. https://www.brooksuspension.co.uk/m...-fz6-600-fazer-yss-mz456-shock-absorber-04-10

 

[Gary in NJ]

I think that is a great find, and will be of high interest to forum members. It seems to be a knock-off of the Ohlins S46/YA403 shock - a unit that now sells for $700 US. Some quick analysis:

The OEM shock is 305mm eye-to-eye, this unit 300mm. Not a big deal, raising the forks in the triple clap a few mm would off-set this. The other thing to note is that the spring rate is 150 N/mm (15.3 kg/mm). The OEM rate is (which is very light) 123 N/mm (12.5 kg/mm). I'm 170 pounds and use a spring rate of 137 N/mm (14 kg/mm). The spring rate at 150 N/mm is sized for someone who weighs around 220 pounds. So if you weigh in that range, this shock is a straight bolt-on. If not you need to account for a new spring. It is possible that Brook will install a proper spring prior to shipment. Ohlins includes the proper spring rate for the rider in the $700 cost...so if Brook charges for a spring swap - the value (and savings) of the YSS may not be there.

The Ohlins comes out of the box ready to use. If the YSS needs a new spring ($100-$150 for the spring) and you have to pay to have it installed (maybe $50-$100) - then there is no point in buying the YSS. Another thing to consider, while Ohlins KNOWS how to properly valve a shock for compression and rebound - YSS products are known for being "close, but needing some work". So if you need to pay someone to respring the shock, you might as well have it serviced too. Now the YSS shock will cost you more than the Ohlins.

I would contact Brooks and see if they provide a spring swap in the price, or see if it can be done for less that $100. If so, there is value.

 

[Abiram Menon]

Hello Gary, Thank you for the detailed post.

YSS is considered an above-average brand here in my country, as many after-market shock absorber swaps are being made on Yamaha's lower-segment motorcycles and scooters. But I am sure they need a better presence in something like a supersport category and above. Ohlins are the supreme champions in this department, but they also cost a lot more. I had all the plans to get the Ohlins, but then I thought of not investing much money in a motorcycle that is 15+ years old.

As you mentioned, 300 vs 305mm will make little difference, but I will also consider lowering the front forks by 5mm. I guess the most significant threat will be GC lowering to 140mm, and we have to be careful about it. Now comes the critical part: stiffness and spring rate. I weigh around 165 pounds and suspect the 150N/mm will be stiff to start with. But does it have anything to do with the preload adjustment? I mean, if I am on the softest setting, will I still feel it as stiff?

But yeah, if it gets complicated, I'm glad to rely blindly on Ohlins and call it a day.

 

[Gary in NJ]

I’m not advocating that you get an Ohlins shock…they are painfully expensive. I’m just cautioning you that the budget shock may cost you the same or more to get it correct.

Preload does not affect spring rate. It is used as a means to adjust suspension sag. The spring will have the same rate whether fully extended or half compressed.

That spring rate is too high. See if the seller is able to provide an alternative rate.