something good:
Thats right newmercman but not sure reducing pressure is good for anything.I have been looking at tyre wear and steering geometry on Scanias for many years now and I have learnt a lot. I would be interested in hearing from any other Scania owners that can share some data.
Even I am amazed by the tyre wear I have acheived with my latest settings and I actually can’t believe that the changes I’ve made have had such a big effect.
Anything you want to share?
Hi 143, yes I have something to share but I don’t expect it to be a one way street. Got any figures for me?
a firm I often work for run 8 rigid 8 wheeler tippers which are all scania they range from brand new to 08 reg they all work quite hard and without fail the front steer will always wear out before the second steer, they used to run Volvo 8 wheelers which were the other way round wearing the second steer first.
Various makes of tyre are used, Goodyear, Bridgestone, Hankook, Continental which all seem to last about the same time though when the casings go for re - moulding for use on the drive axles the Goodyear casings cause the least problem as of yet not one has never been rejected!
Thanks moose that’s interesting. I know Scania go the extra mile setting up their 8 wheelers as they have had so many problems with them in the past. Wearing the 2nd steer first could be tracking?
^^^
Yes and No. Both steering axles need to be set to the correct toe in/out, but also set parallel to one another and to the rear axles. Going back a long time to when I used to do PDIs this check was rarely done, mainly because the dealer didn’t have decent equipment to do it. It was a time consuming business to get right whatever method was used, but what was noticeable was that few vehicles came out of the factory set up correctly. Nowadays with laser alignment equipment it is a much simpler task. There are several companies who will do on site checks and rectification for a very reasonable fee.
However this is a complete waste of time if the vehicle has other faults. I am bound to miss something off the following so I will apologise now.
As has been said previously once a tyre starts wearing abnormally it will continue to do so. It is surprising how out of round cheap tyres can be either initially or shortly afterwards, so jack up the axle and spin the wheel with an axle stand placed ahead of the tyre and almost touching as a guide marker. If any of the axles are allowed to run crab due worn suspension or locating devices then this will affect tyre wear. Likewise worn steering linkage components and shock absorbers have an obvious effect. The dampers on most vehicles are only ever replaced when they either leak badly, or the shrouds rot away; knackered they allow the axle to bounce. You only have to look at how much the air suspended trailer axle you are following oscillates to realise just how hard they are working. Some vehicle makes are particularly susceptible to wear in the second steer relay arm pivot bearing. So assuming the tyres are all OK then apart from the correct pressure for the load to be carried then it is important that the airbag pressures are correct for the axle load. This being particularly important for the second steer of a tractor unit, since the pressure is controlled by the load on axle three. If this axle is too lightly loaded then it can bounce and rattle the life out of all its mounting bushes.
Having checked the above and the obvious things like wheel bearing adjustment, brake freedom from binding and that the wheels themselves run true, the wheels can be balanced. This can again not be as simple as it seems, some makes are more tolerant than others to dirt and rust between the mating surfaces; shiny-clean being the desired goal. Rare to find in use these days but balancing machines which work with the wheel still attached to the axle ensure that everything which is rotating is being balanced.
With the simple things checked now take the vehicle to somewhere with a test lane and put all the axles on the shaker plates, which will be when you find out the true extent of any relative movement in the various axle location devices.
Thats right cav551 the main dealers seem to think setting up the steering geometry is nothing to do with them and its odd tyre wear on new(ish) vehicles that I have been looking at.
All that stuff you mentioned about shocks etc is OK if your truck is 5 years old or so but surely you should get good wear on a new vehicle.
There has been another topic about sliding fifth wheels on a different section of the forum. This also will have an effect on tyre wear, owing to the position of the coupling in relation to the axles affecting the proportion of weight carried by each axle. As was pointed out by Juddian in the thread, in practice the distribution of weight is not always what would seem to be logical. Given this factor, and the Scania identified issue of chassis flexing, plus a vehicle which was never set up properly ex factory, and small amounts of wear in a comparatively newish vehicle can have a ■■■■■■■■■■ effect quite rapidly. Once the tyres have started to wear irregularly not only will they continue to do so, but the vibration the worn tyres set up aggravates the chassis component wear rate.
What was that about Scania chassis flexing? Where and what was the solution?
something good:
Thanks moose that’s interesting. I know Scania go the extra mile setting up their 8 wheelers as they have had so many problems with them in the past. Wearing the 2nd steer first could be tracking?
tracking has been checked in the past with the same results, Volvo wearing the second steer first and Scania wearing the front axle first, The Volvo has a wider stiffer chassis with more anti roll bars as standard than the Scania which means they don’t roll as much in the corners though the Scania has less parts to wear out! The main problem with Scania is the poor drop arm set up on the N/S
Thanks Moose, I’ve been looking at the drop arm set up on the Scania but not looked at the 8 wheeler set up - What do you think is wrong with it?
cav551:
^^^
Buried in here:
Sorry for the late reply. Christmas and all that 
- Couldn’t find anything in that file relating to chassis flex or tyre wear?
But I would interested in opinions on this short video https://youtu.be/gJOkL6iOx5o
Cheers. .