How to improve ride quality?

[Brock]

Different need to Chippy's air suspension question.

 

We're looking to improve the ride on our motorhome as it's quite rough on the poor roads we seem to use. We don't seem to bottom out on the bump stops though. Stability is excellent and it rides level.

 

Wheelbase is a short 3m with an Alko rear end. Axle loadings are 2000kg on front and back with loading on rear at 1700kg and front at 1540kg unless we are away for a few weeks.

 

Those excellent chaps at VB Suspension suggest comfort coil springs at the front and if I had the cash, semi air on the rear. However, they cannot be sure this will solve my concern because ride quality is a perception. They're fairly sure full air suspension on both axles will but at somewhere around the £6k, this is not something I can justify.

 

So has anyone found that the VBS approach is likely to improve ride quality?

 

I'm tempted to go with the coil springs at the front and see how we get on.

[Guest JudgeMental]

Maybe a little lateral thinking will save you money? I have an Airhawk for long haul flights, but you can use in any vehicle I guess and move if you decide to change the van! :D

 

link to truck versions: http://www.airhawk.co.uk/airhawk-for-trucks.html

[Brock]

Eddie, might get the missus one for her birthday because she gets back ache and circulation problems on long journeys but it won't solve the poor ride. Our van seats are petty comfy already but its the shock waves through the structure that are making us think.

[Guest JudgeMental]

"shockwaves through the structure" That does not sound right...I'm sure you have checked tyre pressure and suspension is OK? I thought Alko had a good reputation for ride quality :-S. It seems going by the affidavits that truckers swear by these seats (as do air passengers) and i'm sure your ride cant be as bad as an Artic! That being said to get a van riding like a lux car would be a very expensive proposition (full air)

[Mel B]

JudgeMental - 2014-02-11 4:27 PM

 

Maybe a little lateral thinking will save you money? I have an Airhawk for long haul flights, but you can use in any vehicle I guess and move if you decide to change the van! :D

 

link to truck versions: http://www.airhawk.co.uk/airhawk-for-trucks.html

 

How much!!!!! 8-) £199 ... for a blooming cushion!!!! I think I'd try some memory foam first! :-S

[Mel B]

Brock, what MH have you got and exactly what are you experiencing?

[Brian Kirby]

John, it may help if you say what vehicle, what base vehicle, what age, what is the MAM, what tyres, and what pressures you are running them at.

 

I think all vans crash around somewhat on bad roads, and many of our UK roads presently seem to be badly potholed and poorly patched.

 

Your front axle maximum load suggests a "heavy" ducato base which may partially explain the harsh ride, as the actual laden load is well below its limit. The rear maximum seems fairly typical, although the actual load is still well within the limit. If the tyres are being run at 5.5 bar, this will exacerbate the inevitable harshness of the relatively lightly loaded springs. But, without the information, we are all guessing.

[starvin marvin]

When you have considered Brian advice, you could do a lot worst than look at MAD coil springs,these are an add on to existing rear leaf springs, and these become more active as the vehicle is loaded. Did the trick on our Hymer for little money. It stopped us having to change the van due my wife's motion "sickness", never sick just felt queasy all the time with the movement of the vehicle. The AA fit these to their vans, (don't ask me why) BT Fleet do it for them in the East Mids.

[Brock]

Hymer 504 2013. Front tyre pressures 4.25, rear 5.5 bar in line with Michelin's recommendations when I spoke to their help desk.

 

Ride quality does improve slightly when we have a bit more weight but we never take the kitchen sink away with us and about half of our mileage is using the van for day trips. We reckon another 85kg maximum if we went away for a traditional few weeks [based on our experience in the last van].

 

We've had no sudden jarring suggesting we've ever hit the bump stops. The feeling is akin to sudden deceleration rather than a crash! We hit a 'pothole' or similar and the front suspension depresses and rises before the rear axle hits the 'pothole'.

 

My wife, eldest son and I reckon the ride quality is the worse we've had in the 6 vans we've owned. I expected worse stability because of the short wheel base but it is really firmly planted on the road. On a good road, it is a joy to drive.

 

VBS think the new Fiat is heavy at the front - hence the comment about new comfort coil springs. But I need to be sure they will improve the ride before spending money. We can live with the ride.

[gocro]

I agree that you should look for the source of this crashing ride rather than shell out large qualities of money hopefully.

Our Alko equipped Autocruise has the smoothest most stable ride of all our motorhomes driven.

[Robinhood]

Brock - 2014-02-11 8:50 PM

 

Hymer 504 2013. Front tyre pressures 4.25, rear 5.5 bar in line with Michelin's recommendations when I spoke to their help desk.

 

 

....I'd be interested which size tyre (presumably Agilis Camping?) you are running.

 

I appreciate that Michelin nowadays tend to quote fairly high recommended pressures, and particularly for the rear axle they simply stick to the maximum 5.5 bar.

 

IMO, however, this is a prime contributor to a hard ride, especially when the rear axle load is way below that catered for by the 5.5 bar generally quoted (probably exacerbated by a short wheelbase).

 

In the past, they would have quoted much lower pressures for the axle loads you outline, and from experience lowering pressures to such quoted levels has dramatically improved ride.

 

It is possible to determine (implicitly) safe lower pressures from data tables provided in the past by Tyresafe, or indeed by other manufacturer's (e.g. Continental) data for similar tyres.

 

Using these would of course be in contravention of the Michelin quoted figures and thus at least partly at your own risk, but if it were me I would be very much inclined to do at least a short trial if the current situation is as bad as you describe.

 

(As an example, Michelin used to quote 60/64 psi for 215/75 R16 Camping Tyres running at the previous Ducato Maxi maximum axle loads of 1850/2120 respectively - using these pressures, which were still somewhat above actual axle loads, improved the ride on my previous two 'vans tremendously).

 

 

 

 

[Keithl]

Front pressure of 4.25 bar is over 60 psi !!!

 

IMV that is way too high (only my opinion I hasten to add before I get shot down).

 

Try looking up your tyre size and axle weights in the Tyresafe MH brochure and see what pressures it comes up with. Link.

 

The Tyresafe pressures will be an interesting comparison.

 

Keith.

 

[lennyhb]

Tyre pressure sounds right for a Hymer on Michelins, Hymer always quote higher rear pressure for Michelin all other tyre makes rear is 4.5 bar.

Contis would give a softer ride and you could lower the rear pressure, Have you looked at Goldsmitt springs (not sure on spelling) Hymer fit them as standard now on B Class and option on other models, they raise the front end up to give the van a level stance so must have longer travel I think they are around £400 a pair.

 

Edit:

Just noticed your van is 2013 so may have the Goldsmitt springs if it sits level without a front end downward stance it probably has them.

[Mel B]

Keithl - 2014-02-11 9:50 PM

 

Front pressure of 4.25 bar is over 60 psi !!!

 

IMV that is way too high (only my opinion I hasten to add before I get shot down).

 

Try looking up your tyre size and axle weights in the Tyresafe MH brochure and see what pressures it comes up with. Link.

 

The Tyresafe pressures will be an interesting comparison.

 

Keith.

 

4.25 bar = 61.64 PSI to be exact which, even to me who's no expert, seems high. If your tyres are too too 'solid' they won't take out some of the force so more will be felt through the rest of the suspension ... I would therefore suggest you have a go at reducing the pressure a bit and see if it improves things.

 

The other thing I've thought of is to check what weight you have on each of the axles, both in 'potter about' mode and in 'holiday' mode, if you are near the limit on the front and not the rear, this could affect the stance of the MH and therefore increase the 'dipping' effect which you're experiencing.

[Brock]

Lenny, go to the top of the class.

 

I have numerous extras fitted as standard for UK vans including, I have discovered since reading your post, "Special coil springs for front axle, incl. Axle load increase" as part of the Chassis-Comfort Package which costs £1,672. I'm not going to change these springs; that would be a waste of money.

 

We bought the van as already specced because it was the last of the model in the UK and was not going to be imported this year.

 

So sorry to others for wasting their time. I feel a right fool. I should have translated the specification sheet [504 was not in the 2013 UK brochures]. I shall now go and sit in a darkened room as penance.

 

 

[Robinhood]

....with uprated springs, even more reason (IMO) to ensure you're getting the best cushioning from your tyres by running at pressures more appropriate to the axle loads.

 

I appreciate that questioning Michelin's current advice has been (and no doubt will remain) contentious on here, but I still believe that the pressures you are running at for both the front and rear axle loads quoted are way above the appropriate (and safe, as long as you know the actual axle loads) pressures, and will be conducive to a filling-rattling ride.

 

Whether on 15 or 16 inch wheels, at your loads there is scope to reduce both front and rear pressures by a large amount, which should improve both handling and ride.

[lennyhb]

Sounds like you are going to have to live with it John. I assume by the wheelbase it is a B Class (Exsis 504 wheelbase is 3350). It is a very short wheelbase I take it it is also a very choppy ride on rough surfaces. Any sort of suspension aid will only stiffen up the suspension the full air system is the only option lightly to work and then you wouldn't know until you have spent the dosh. Hind sight is wonderful the full air option from Hymer is only about 3k.

[Keithl]

Brock,

 

It seems to me that you are running your tyre pressures at high figures to suit maximum axle loadings. Have you tried asking Michelin if you can lower them to suit your ACTUAL loadings? This may give you a slightly softer ride. I also assume you have Camping (CP) tyres by the pressures you have given.

Or try lowering them according to the TyreSafe brochure just for a test run before consulting Michelin as to long term pressures.

 

A final option may be to switch to C (White van man) tyres as these tend to run at lower pressures than CP, but this would need loads and pressures checking very carefully.

 

Keith.

[Robinhood]

Keithl - 2014-02-12 1:42 PM

 

Brock,

 

It seems to me that you are running your tyre pressures at high figures to suit maximum axle loadings. Have you tried asking Michelin if you can lower them to suit your ACTUAL loadings? This may give you a slightly softer ride. I also assume you have Camping (CP) tyres by the pressures you have given.

Or try lowering them according to the TyreSafe brochure just for a test run before consulting Michelin as to long term pressures.

 

A final option may be to switch to C (White van man) tyres as these tend to run at lower pressures than CP, but this would need loads and pressures checking very carefully.

 

Keith.

 

....I interpreted a previous post as confirming he is running at Michelin recommended pressures for the quoted actual loads.

 

The problem is that though Michelin used to quote lower pressures based on actual loads (consistent with the Tyresafe data and other manufacturer's tables), nowadays they tend to quote somewhat higher pressures for the front axle, and the maximum tyre pressure (5.5 bar for a Camping tyre) only for the rear axle, regardless of any (sometimes much) lower actual load.

 

My experience is that they used to quote at or around the Tyresafe data for actual rear axle load, and roughly 10% higher than the data would give for the front axle, to allow for weight transfer under braking.

 

Possibly apocryphally, the 5.5 bar level is rumoured to have been set as a safety measure to allow for the alleged widespread overloading of rear axles found on motorcaravans, something that patently does not apply here.

 

IMO, therefore, the pressures would be better set at levels closer to those set out in the Tyresafe document.

 

In reality, prior to the change of stance set out above, the pressure/load profiles for C and CP tyres varied very little (indeed, not at all for front axle use), though Continental (in parallel with the Tyresafe data) do (did?) quote a steeper pressure profile for rear axle use for Camper tyres, but also do (or at least would) still quote a specific pressure against axle loads for the rear axle (which could still result in recommendations well below 5.5bar).

 

Running a tyre at higher than optimal pressure will affect ride, handling and tyre wear, and also reduce the "footprint" in contact with the road, affecting both grip and braking. It would appear that Michelin may have balanced the risk of the "safety related" factors in this against the risks of overloading, and decided that quoting the higher pressures is the lesser of two evils.

 

Patently, this leaves one with the less safety related issues of tyre wear, handling and ride, something you have to live with every day, but Michelin don't.

 

I'd still reduce the pressures to the Tyresafe values (possibly adjusting the axle loads +10%), and give it a try - my money would be on a noticeable improvement.

[mikebeaches]

I agree entirely with Robinhood concerning tyre pressures and the Michelin advice. As he said, they used to advise appropriate pressures for the load on EACH axle, but will now only do it for the front. The rear tyres are almost certainly way too hard at 5.5 bar.

 

When I purchased my van new I had to drive 60 miles on the motorway to get home from the dealer. Obviously, the van was not loaded, but the tyres were set at 5.5 bar all round. The ride was frightening and the van kept wandering all over the place, especially when it got into the 'tram lines' in the nearside lane.

 

Thankfully, adjusting the pressures down, sorted everything out - although the ride remains more harsh than I'd like.

 

Mike

[Derek Uzzell]

Assuming Brock's Hymer's tyres are Michelin "Agilis Camping" pattern in 215/70 R15CP size. appropriate inflation pressures for the quoted 1540kg(Front) and 1700kg(Rear) axle-loadings would be around 3.4bar (50psi) and 4.5bar (65psi) respectively. Those pressures are extrapolated from Continental's data for 215/70 R15CP "VancoCamper" tyres.

 

The 3.4bar/4.5bar pressures err on the 'safe' side and would be worth experimenting with by, say, driving the motorhome over a rough road with the tyres at 4.25bar and 5.5bar, then repeating the same exercise with the pressures reduced. If the vehicle is 'hard sprung', dropping the pressures should not be expected to effect a miraculous improvement, but the experiment would be worth trying.

 

 

[Brian Kirby]

Following on from Derek's post above, if the Tyresafe data (published by the British Tyre Manufacturers' Association, of which Michelin is a long standing member) is used in lieu of Michelin's, for the same tyre size and loads, the result would be front 4.0 bar (58psi) (the table doesn't quote CP tyre pressures below 4.0 bar) and rear 4.25 (62psi) bar. It might be instructive to contact Michelin technical and ask them if they resile from the published Tyresafe pressure recommendations, rather than asking them for their own recommendations. Obviously, these pressures are above continental's for equivalent rated tyres of equal size, but they do accord with published data to which Michelin apparently subscribe.

[Brock]

Oh, I am grateful to this forum.

 

I've communicated with Hymer and Gold Schmitt in Germany who were helpful. I've changed the way we load the van to increase the weight on the front axle. Even so, in 'winter motohoming trim' we are still lighter than the weights I quoted before. With this information, your comments, and a new weight certificate, I went back to Michelin. I'm now running at 3.9 bar [57psi] which gives me a reasonable ride and does not seem to adversely affect my fuel consumption. I can go lower if I'm just using the motorhome for day to day travel. I will go higher when in full touring trim.

 

VB Air Suspension have also been helpful and did say they would check the front suspension before doing any work to ensure they were not replacing like with like.

 

Overall, I've probably saved between £400 and £800 and have a better understanding of how my van works.

 

Not a bad return from a free forum!

 

Thanks.

[Will86]

Choose your next vehicle with a longer wheel base !

[Brock]

Just under twelve months after my last post, I succumbed to the allure of semi air suspension on the rear axle. I couldn't justify full air for the use we make of the van.

 

I'm now running at 3.65bar at the front and 5.25bar at the rear with 'approval' from Michelin.

 

I went for the semi air suspension from Goldschmitt fitted by Travelworld to complement the heavy duty Goldschmitt springs on the front. I was pleased with Travelworld's work.

 

Does semi air work? Well, a few thousand miles and 3 months of running at almost full 3500kg weight, 1850 of that on the rear, and it still feels better The bangs and crashes have reduced significantly although a few rattles still persist.

 

My Transit driving son followed me out of an industrial estate and over 4 speed bumps that were as steep as a standard roadside kerb. He said that the van still crashes a little at the front but the rear coped serenely with no sign of shudders through the body work. It was clear to him that the semi air was working to contain the bumps. He also noticed my van tilted from left to right. Silly me had emptied the garage of all except the spare wheel on one side.