Best suspension upgrade for a GSX-R750?
24 September 2012 16:35
Q. My GSX-R750 K2 is now 10 years old (obviously!) and has nearly 35,000 on the clock.
Everything I read about 'suspension' says it will need replacing or refreshing after about 16,000 miles, so I can only assume mine is most certainly well past its best and I am riding around the ‘wear and tear' characteristics?
I am considering new progressive front fork springs and oil and new a new rear Shock, both by Hagon. Also new swingarm bearings. Is there anything else I should consider?
By the way I only ride on the road and it's mainly a mixture of fast sweeping B Roads and more 'nadgery' stuff, so a compromise in overall setting is probably inevitable?
A. All round suspension service and rebuild will make a big difference to the way the bike feels – like cosmetic surgery combined with many trips to the gym – it will look and feel a lot better.
We spoke to Dave Parkinson at DIP Racing (firstname.lastname@example.org or 0033-682-709627) for his take on a suspension makeover:
“The standard Kayaba rear shock is a decent bit of kit, but the Teflon-coated DU bush that slides up and down the damper rod will need replacing, as will the rubber seals and any shims that look worn.
“The spring might look cruddy, so a rub down and respray is always nice, but it won’t have lost have lost its power, apart from settling slightly, which is why older bikes need a bit of rear preload dialed in after 10,000 miles. 3.5 to 5 weight good quality suspension fluid is a must.
“This set up is good enough for track work, if you were really into the circuits, a bit more high-speed rebound damping would give you better tyre wear.”
The front forks are Kayabas again, and have good quality 20mm cartridges in them that are the same as the race bikes of that era, so you are starting from a good base.
Progressive springs might have their place on a touring bike floating over poor surfaces, but on a sports bike the feel close to the limits of your ability of the bike’s tyre grip is what really matters.
Linear-rate springs will deliver more consistent feedback of what’s happening at the sharp end when you keeled right over and almost fully committed, according to Dave. If you are pushing 15 stone go for 0.95kg/mm up front, if you haven’t got a belly 0.90kg/mm springs will support you.
The aim of a fork service and rebuild is to give you finer feel and also a wider range of adjustment, but you can stick to the standard shims and run 7.5 to 10weight fork oil.
“The advantage of a re-shim is that the oil passing through the cartridge is being metered better, is more controlled so you can run a lighter weight oil, which reacts quicker itself, giving you the feedback you need at 80mph through a bumpy right-hander.” Says Dave.
Prices vary in the industry, but a typical price is £90 plus p and p for a shock rebuild, £90 for a fork service and £200 for a fork service and rebuild to your requirements.