Suspension advice & answers needed

[Bendeigid]

Hello, I hope, I posted this in the right forum. If not, please move it or let me know. Sorry, in advance, for the long-winded nature of this post; I just thought, that it would be best to ask all of these in one post, to be able to keep track of it and hope that some might take the time to answer either some or all of it. So here it is:

 

This year I will have to do some work on my suspension for the first time since college over 20 years ago. I can only do my work outdoors on my drive-way, since I do not have enough space in my garage. Therefore, my approach will to replace existing with 'new' (or repaired/restored) items, which, while more expensive, at least should mean, I can do most of the work in stages and put the bike back in the garage overnight. 

 

My bike is almost 26 years old by now, and I am not using it that much due to a few things, that are not really worth mentioning here. The only riding I do, is on the road. So, the main bit for me, is to keep the cost under control, while getting the most benefit out of it. My thoughts would be to go for mid-tier items rather than cheapest or most expensive, if that makes sense.

 

Now, here are some of my questions regarding that (also, any advice is welcome).

 

1. I need to replace at least fork oil, seals and bushes. Is it better to get one of these kit that include everything? And if so, what manufacturers are good and which to avoid? Or is it better to buy OEM items (keeping in mind that they seem quite a bit more expensive)?

 

2. While I am in there, I thought it might be an idea to replace fork springs. Are progressive springs much better than OEM (which feel quite soft, as the bike likes to sag quite a bit when breaking at lights)? Again, which manufacturers are good, which to avoid? Prices, as far as I have seen, seem to be fairly similar.

 

3. Is it really that important to adjust the spring rate of the fork springs to your weight? I have only seen about three different rates at most, and some don't even seem to come in different rates. If weight should be taken into consideration, do you aim for your weight including all the usual additions, like clothing, helmet and usual luggage, or should you add some extra for when more luggage is carried or weight gain/loss and how much(i.e. in my case, I mostly have a small tank-bag with me, but maybe sometimes I carry a backpack with items, which I do not know the weight of beforehand)?

 

4. I also saw something called fork cartridge emulators, that some think is a worthwhile upgrade for these old type forks (damper rod with the stanchions on top). Has anyone any experience with them? I have only found two manufacturers that seem to make them (YSS @£90.- & Racetech @£200.-). Are there any others? I know there are cartridge inserts for certain forks, but at a cost that I do not think is reasonable for me.

 

Now to move to the rear shock:

 

5. I have found three manufacturers (YSS, Hagon & Nitron) that do shocks for this bike and are about the price range (£500 - 650) I would consider for me to be reasonable (keeping all the points in mind, that I set out above). Are there any other manufacturers out there at my price point? Are the ones I listed any good (reliability, quality, adjustability)?

 

6. I suppose the same questions as for point 3 apply here.

 

7. Would or should you change the bearings for the swing arm and cushion lever, while changing the shock? 

 

Thank you to everyone that has taken time to read and/or answer/give advice.

[Nick the wanderer]

Hi welcome,

a lot depends on how you want to ride it for me. If you push on and like a bit of scratching go for all you can afford. 

For a basic fork refresh, seals and oil, shouldn't be that expensive. I think you may be surprised what a difference that would make. Depending on your weight you could use a slightly heavier oil, or not.

Your weight varies greatly day to day. I go for an average weight with kit on. Don't overthink it.

I'd start there if I was you. 

[Tinkicker]

Nick is spot on.  When I was younger and used to hoon around with my hair on fire, on rides out with a very competitive bike club; I used to set great store in getting the sag right and using different weight oils.

 

These days if the oil stays in the forks and the shock damps, I am good to go.  As an old bufoon, I rarely overtake invalid carriages these days.

 

As for the rest of your questions.

Hard to answer since we do not know why you deem your suspension to be in need of an overhaul, nor what make and model your bike is.

If it is a Honda RC45, you would receive very different answers to if it was a CG125.

 

As a general rule, always go for OEM parts for forks.  

 

Rear shock.  I put a new Hagon shock on my VFR750 during its restoration and never bothered altering its settings.  Its fine.  YSS are gaining a good rep too.

As for bearings ect.  Do they actually need replacing or just a good clean, regrease and new seals?

[Stu]

As has been said it depends on the type of riding you are doing 

 

I put progressive springs in the FJR and springs to me weight in the TL1000s that I had! both different bikes and both ridden differently but what I did notice is that for me the progressive springs where better for the road

 

Rear shocks! For the TL I had a Bitubo shock which worked well but was expensive I then used a modified R6 damper with the stock spring and that was a huge improvement. On the FJR I replaced the rear spring using the stock shock again for a progressive one and that worked well too 

 

As for components I would use as much OE stuff as possible especially seals and bushes if you get Hyperpro springs they will come with their own oil and recommendations. When it comes to oil weight tread carefully as its not about the weight of the oil but on how it flows through the valves there is some good reading on viscosity and centistokes but its a minefield! usually its best to get a package from a specialist who has done all the leg work already 

 

You adjust springs to your weight and not the oil! the oil is there to control the speed that it moves! let the springs to the springing and the holding of weight and the oil do the controlling of the damping 

 

For rear shocks I would be looking at either nitron or hyperpro and hagon and YSS if budget can't stretch. All good shocks the first to are a bit better though 

 

Oh and weight is measured in all your riding gear 

[Bendeigid]

Thank you for your answers so far. Certainly gives me some more info. 

 

I only do road riding at or below speed posted, as I am getting into middle-age by now and like to enjoy the road and scenery as much the ride itself.

 

@Tinkicker: Bike is Suzuki GSX750F from 1998 and I have not looked at those bearings for the last 20 years or the suspension much, other than to ensure there are no leaks or corrosion/pitting on the swept area of the stanchions. Passed MOT 2 years ago (have not really used it last year), but that does not necessarily say a lot about the state of them. On this bike there are no seals on the bearing, as far as I am aware, since they are all needle roller bearings.

 

Fork seals on mine are starting to come apart and have just bought some forks from EBay that look ok (have not received yet), but also need new seals and oil, and since I can't say anything about the rest I think it is safer to assume that bushes need replacing too.

 

The rear shock got some issues with powder coating on the spring coming off due to rust underneath on the spring itself and bottom adjuster has not worked for quite a few years. 

 

@Stu: Hyperpro does not seem to make shocks anymore for this bike only progressive shock springs. It is all a bit of a minefield and trying to find info about suspension without requiring a university degree in physics and mathematics seems quite difficult.

[Stu]

@Bendeigid In that case just stick with one of the 3 you have mentioned 

 

Does YSS and Hagon spring to your weight? 

 

Although saying that you are riding within the limits on the road and probably no need to go that for 

[RideWithStyles]

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Edited May 15, 2024 by RideWithStyles
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[RideWithStyles]

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Edited May 15, 2024 by RideWithStyles
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[RideWithStyles]

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Edited May 15, 2024 by RideWithStyles

[NewToN]

Refreshing the suspension makes a massive difference to an older bike especially if it hasn't been touched since it was manufactured.

 

Starting with the front forks first stick a tie-wrap around one of the stanchions. Determine topped out position (wheel off ground), then how much it compresses under it's own weight (static sag) and how much it compresses with you sitting on it (rider sag). Also leave the tie-wrap on and go for a ride at you usual speed include some bumpy roads and some reasonably hard front wheel braking. When you get back see how much of the total travel you have used. The rider sag and the travel will indicate whether you need different springs to suit you weight/riding style.

 

I would suggest to strip the forks first. If the oil is really old (dirty and smelly) you need a full strip and clean and probably new bushes too. However assess the bushes based on wear (they change colour as the anti-friction coating wears away). You need to look at the stanchions to see if they are pitted (bad pitting will mess up new seals and bushes) and if so either replace or re-chrome them. When you put them back together new oil will significantly change how they feel if the old oil was in bad condition. So its not always easy to judge what to use as new will feel different to old. Initially go with manufacturers recommendation (if available) otherwise choose an oil with the same viscosity (like 37cSt at 40degC) not one with the same nominal weight (like 10W). For seals and bushes I find All Balls Racing kits to be good value for money.

 

While you have the forks out disassemble the steering head bearings. If they are undamaged then regrease and preload them. If they are original they will almost certainly need replacing.

 

At the rear I think the GSX750F has a linkage similar to the Bandit in which case the rocker arm bearings may be corroded/seized (assuming no previous maintenance). You will need to replace the needle roller bearings and the pins/rings that run in them if they are grooved/corroded. It's worth taking the swingarm off to check the bearings if only to regrease them if in good condition (like steering head). If you are replacing the rear shock it will make a huge difference but be aware of the different types. All are gas pressurised these days but it is done in different ways at different price points; emulsion (where oil and gas are mixed), a bladder (gas in bladder not mixed with oil), a floating piston (gas separated from oil with a floating piston). Bladder and floating piston types sometimes also use a separate canister. Examples: emulsion - YSS and Hagon, bladder - M Shock, floating piston - Nitron. In addition to those you listed I suggest to consider the M-Shock (google Shock Factory UK).

 

[Bendeigid]

Sorry for not getting back earlier. I had read the posts, but have been unable to get answers together and I could not find my service manual.

 

@Stu I have not checked on that. I actually found someone that still sells Hyperpro shocks for my bike. I do not know if they are old stock or if Hyperpro just does not list them any more on their website.

 

@RideWithStyles From what I can recall (more than 20 years ago), the suspension has always felt a bit on the soft side. Back then, I had tried some different settings, but they did not seem to make much of a difference. The suspension has not been serviced (yes, I know, bad) but I checked externally on it for any leaks and/or drips. The settings I am using are the standard settings as according to service/workshop manual (front 3rd click, back rebound 2nd click & compression 1 3/4 turns out). However, the rebound adjuster just seems to spin nowadays without any engagement.

 

To 2. The diagram does not show much regarding the springs used, but a note in the service manual seems to suggest that they might be progressive springs ('Note: The end of the fork spring with the smaller pitch should be at the bottom of the front fork.')

 

'If of you keep the std valves ( elm compression and rebound) i wouldnt just put liner springs in.' Could you please explain more what you mean here, as I don't understand?

In regard to fork oil thickness, this is info that I was not aware of at all. I had assumed that there would be some kind of standardisation. How are you ever supposed to figure that one out without trying them all out? Especially since the service manual only says 'Fork oil type: Suzuki Fork Oil SS-08 (#10) or equivalent fork oil' but gives no further information on it.

 

Tyre tread wear pattern seems to indicate even wear.

 

@NewToN When I read your advice how to measure suspension travel it came back to me (I believe they might have taught that at college). However, I have something like a chicken-and-egg situation since the bike has no MOT at the moment and is SORN'd I can not take it out, and I really need to do this work before putting it in for an MOT.

 

I have inspected the 2nd-hand forks I bought for this job, and they seem to be perfect externally (no corrosion on the stanchions at all and the lower legs are in much better condition than mine). I have not yet taken any of it apart; so I can not say anything about the internal wear.

 

The steering head bearings should be fine (I would hope; they are 'original' from when I bought the bike over 20 years ago) as there is no binding or notching over the range of movement but will have a look when I get to it.

Where can you find any info in regard to the viscosity of the oil that Suzuki recommends (Suzuki Fork Oil SS-08 (#10))?

 

Thank you for the information on rear shocks. Something else I had not considered, especially since some do not even seem to list that information (or at least not clearly enough for me to understand easily). Would an emulsion type not separate after sitting for a while and possible cause issues then?

[Bendeigid]

Another question into the round: How often would you change the oil in forks (miles or years) as it there is no mentioning in the service manual other than check externally for any signs of leakage or wear?

[husoi]

1 hour ago, Bendeigid said:

Another question into the round: How often would you change the oil in forks (miles or years) as it there is no mentioning in the service manual other than check externally for any signs of leakage or wear?

Depends on what parts you change when servicing the forks

 

Simple oil change I would say every year with service.

If replacing bushes and other parts I would inspect every 2 or 3 years with annual oil change.

[RideWithStyles]

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Edited May 15, 2024 by RideWithStyles
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[oldgrump]

Hi @Bendeigid,  Looks like you need to change the Fork oil at least, as for 15 weight, I personally think that's to high, I've never used 15 apart from Heavy Cruisers, for a road bike like the Gsx750f I would use 10 weight.

 

My 97 VFR800 runs Hagon fork spring and 5 weight oil, always 2 up and fully loaded, change fork oil every 2 years which is about 20000 miles now.

 

Rear shock is a Hagon, had that serviced by Hagon after 35000 miles when it lost its damping. Owned the bike for last 96000 miles never stripped forks down, only changed springs, so as far as I know still running original fork seals

[_amw_]

I'm no suspension expert, but I can certainly agree that changing old fork oil for new can make things a lot better.

 

Given what you were saying about lack of MoT I would aim to get an MoT ASAP so that you can test the bike on the road - maybe put off some of the work 'til later (unless it is needed to pass the MoT?).  This will mean you can refresh your memory about how it handles and appreciate the difference that your hard work will have achieved.

 

Personally, given how much difference new fork oil made on my (knackered) bike, I'd suggest that you just do that to start with and go from there.

[RideWithStyles]

man...

Edited May 15, 2024 by RideWithStyles