How to: fit a BMW s1000rr rear shock to a VFR 400 nc30

[speedy231278]

You can have my BMW spring if you need it dave

Cheers trig, bit of yellow paint and no one will ever notice

Unless it's for use inside tunnels...

[john alex]

do you have to cut the under seat tail unit mudguard to fit shock

[porndoguk]

do you have to cut the under seat tail unit mudguard to fit shock

Nope

[speedy231278]

So, apart from having to shave the top shock mount, and the back of the undertray mount, it will literally bolt straight on to an NC35 save for having to re-spring? What mods would have to be made if you were to consider fitting an HRC linkage, assuming it would fit?

[Drunkn Munky]

From what i can work out fitting the HRC linkage changes the way the shock works, the main thing is it will allow you to use a softer spring which is a good thing as nearly all shocks are valved to run softer springs. You will then need either a adjustable length shock or a adjustable pull arm(dog leg link) or both if you want to get it spot on.

Ive no idea how the right spring rate and pull arm length is worked out im just going on what 999gomez has suggested as he seems to have plenty of experience with this setup. Its what im going for on the trackbike, for starters its HRC so it must be good and also the ohlins shock i have for it is fitted with a softer spring so is likely to already be valved right saving me money having that done on top.

[speedy231278]

Isn't it the same as the road linkage, just with a slight change to the dogbone length? Somewhere on here someone posted pics of one where they'd welded up the original holes and 'moved' them a few mm. Given that I'm a year-round rider who spends winter tootling about in shite weather and only get to ride a bit nippier (never over the limit m'lud) during the summer, ultimate trickery and perfectly sorted linkage ratios aren't exactly a make or break thing. However, seeing as the all-dancing version of the Nitron shock that I'm considering weighs in at about £550, when the BMW unit is about a ton, plus about half as much again for the spring, it makes lots of theoretical unspent wonga spare for the HRC linkage. BUT... I don't really like the idea of filing the shock mount, or the frame, nor the possibility that I might find that while the HRC linkage fits, and the BMW shock fits, the linkage AND the shock cause issues that can't be resolved, all for the 'saving' of about a hundred quid.

Does the HRC linkage need a different length shock, and what would it do to the spring rate? If it makes it softer in effect, would that mean that assuming both fit together at the same time, it might not be as critical to have the shock re-sprung? Too many unknowns... and too many unknown unknowns... lol

[Drunkn Munky]

I think your confusing the HRC linkage with the re-drill link people do to compensate for the height loss when switching from a 18" to a 17" wheel on a NC30. The fancy billet HRC linkage rick o sells is both the pull arm(dog leg) and triangular link, both are different spec to the stock items therefore needing a different spec shock ie a softer rate spring.

I agree info on this setup is surprisingly thin on then ground and its also unclear which one rick has made a replica of as HRC spec two different lengths, one for a 18" wheel and one for a 17" wheel. However as i said above 999gomez has the HRC linkage that rick sells and i belive had some input into the design so im trusting in what he says should work with regards to shock length, spring rate and pull arm length.

Taking into account your situation and what you intend on using the bike for your best bet would be to just buy a decent NC30/35 specific shock and forget about the HRC linkage, thats what 99% of people inc racers are doing and have been for years. It works and works well although what 999gomez has said earlier in the thread regarding the stock setup's pitfalls makes perfect sense, the only reason im opting for the HRC setup is im trying to build a bike as close to HRC TT-F3 as i can plus im a serial tinkerer and find it near impossible to leave stuff alone when theres a chance i can improve on it

[speedy231278]

Ah, right, I thought that maybe the HRC linkage addressed the issue of the changing ratio when the shock was compressed.

[Drunkn Munky]

It does.

[CMSMJ1]

^ that is the point of it. A normal linkage has ot accomodate a 7st Japanese weakling driving an 850lb shock spring and valving to match....or it has (in the past) had to put up with my fat arse and the lady wife as pillion too!

it needs to have a rate that stiffens as it runs out of travel..which is a bad thing when you are racing and need the stroke to be more linear and more finesse.

I run an RS250 shock still...it is cool. works lovely. I am finding out that I obviously need a new linkage and some adjustable 'bones too...