Surely a bearing tight enough to have an effect on mpg is going to fail before you can check the mpg .
I run 8 wheel hook loader’s with tandem axle trailers,so not the most aerodynamic vehicles, fuel consumption this week,
Dafs are between 8.53 and 8.90, these are 85-460’s, mileages between 280,00 and 350,00 kms
Scania’s,are smack on 8.3, these are R450’s, mileages between 575,000 and 610,000 kms.
They run 60% motorway and rest A roads and on and off landfills a couple of times a day. The Daf’s are higher geared and 56 mph is around the 1,100 rpm mark whilst the Scania’s are on 1,500 rpm at 56 mph. All the fleet don’t exceed 13 foot overall height.
Punchy Dan:
Surely a bearing tight enough to have an effect on mpg is going to fail before you can check the mpg .
Any resistance at all increases drag, any reduction in drag, however small, will increase mpg.
Cheers for the replies fellas, some good information,
My area is a mixture of A/B roads, duel carriage ways, and motorways, and all loads are relatively short journeys, i previously had a 11 litre scania on the same work, and it was achieving high 8’s day in, day out.
I have a mate with the same motor, and his has been mapped, but his is doing mid 8’s, on similar work, ive mapped mine as well, i got an improvement of around 0.2mpg, so next thing is a top end set up, and full wheel alignment, Ive heard good reviews about Feather diesels up in Leeds, has anyone got any experience with them?
I had a 143 fettled at Feather Diesels, it was money well spent, turned a donkey into a racehorse.
I fit wheel bearings most weeks and still don’t understand how you make sure a non adjustable cartridge type bearing is set up correctly ?
Please use larger letters!
Moose:
I fit wheel bearings most weeks and still don’t understand how you make sure a non adjustable cartridge type bearing is set up correctly ?Please use larger letters!
My understanding of a wheel bearing is that one side of the bearing race will be attached to the fixed axle, the other side to the moving hub, in between these parts are the bearings, so far, so good. Now to stop it all coming apart, the bearing race over the fixed axle will be secured to said axle by a nut. Leaving this nut too loose will allow lateral movement and corresponding friction. Over tightening this nut will misalign the two bearing races creating lateral friction on the bearings inside.
Maybe the reason you’re changing wheel bearings so often is because they’re not being fitted correctly in the first place?
I think that a lot of modern wheel bearings are non adjustable, you just torque the nut up and that’s the job done. Many car rear hub bearings are similar, infact on certain French makes the hub plus bearing and brake disc comes as a complete unit and the bearings and disc cannot be seperated from it. Faster assembly time is the reason given, expensive when just the disc is worn though! 
Pete.
I strongly suspect the original posters vehicle will be fitted with non adjustable cartridge type Pete
During my work I come across all types on trucks and trailers, modern press the cartridge into the hub and torque up the hub nut type and the inner and outer taper roller bearings that have been used for donkeys years.
Due to the type of work we do and the fact that we run many low bed trailers with small wheels and drum brakes bearings are checked for adjustment at every service.
When the brakes are re lined the bearings are usually removed washed out checked and re packed with grease.
We don’t have much wheel bearing trouble as we keep the ones you can adjust in adjustment and correctly greased and the ones you can’t adjust get checked for play and noise.
I’ve never heard anyone checking wheel bearings adjustment for fuel economy!
To set my mind at rest at brew time in the morning I’ll ask the chap I work with who’s been a commercial vehicle fitter since 1974 if he’s ever come across it, lol
I’ve a good idea what he will say, I’ll obviously let him know that an ex pat who’s already conquered the Uk and most of Europe, along with writing various truck magazine articles is offering advice based on his own understanding and not experience direct from his State side operations.
If that pleases you Moose, you go ahead, knock yourself out mate. The fact remains, an incorrectly adjusted wheel bearing will create friction, friction requires force to overcome, this force comes from the combustion of diesel, less friction from correctly adjusted bearings requires less force to overcome it, therefore less diesel is required. The same applies to rolling resistance.
Yes, I have owned and operated lorries in the UK, Europe and North America, I have also been a full time road tester and staff writer for TRUCK magazine and had a long running (10yrs) monthly column in a Canadian trucking magazine, what’s your gripe with that?
Here you go Moose, have a read of this, the boys and girls involved are experts in bearings or fuel economy, so I’m inclined to believe them more than some random bloke off a forum, even if they have written for a magazine or been on the spanners since 1974.
[fleetimages]
Joel Morrow says adjusting his wheel bearings to a slight preload condition helped him improve his results in the Run on Less fuel economy challenge.
Photo: Schaller LL
We have seen some compelling but anecdotal evidence suggesting that wheel-end tightness can affect fuel economy — sometimes significantly. Joel Morrow, head of research and development, Ploger Transportation, has posted on Facebook about his experience with wheel bearings. He claims that the difference between factory-tightened tractor and trailer wheel bearings and those adjusted to a slight preload condition with a special tool produced a before-and-after improvement of 1.4 mpg in testing done prior to last year’s Run on Less fuel economy challenge sponsored by NACFE (the North American Council on Freight Efficiency).
We are not aware of any testing on wheel-bearing adjustment done to prescribed standards, but Morrow says bearing adjustment on new vehicles straight from the factory is inconsistent.
“We just took delivery of 10 new [tractors], and on two out of the 10, every wheel-end on the truck was too tight,” he says. “Most of the trucks had one or two wheel-ends that were too tight. On two other tractors, all the wheel-ends were just fine. Trailers are even worse than tractors. It’s not uncommon among a group of new trailers to see half of the wheel-ends too tight regardless of the supplier. We’ve seen this condition on several different brands of wheel-end. There’s just no consistency in that adjustment.”
Morrow says the condition is associated with the pre-adjusted bearing and hub assemblies that use a spacer to maintain bearing tolerance following a prescribed tightening procedure with pre-determined torque values. He suspects there may be some calibration issues with the tools used to install wheel hubs at the factory.
Bryan Williams, ConMet’s vice president of engineering, adds, “Proper torque at the factory is critical to ensure the bearing adjustment is correct. If the torque applied was too high the bearings can be put into excessive pre-load, or if the torque was too low, the bearings can have excessive endplay. Both of which could affect fuel economy and the performance of the bearings over time. Typically, wheel bearings have very limited impact on rolling resistance, however many alternative factors, including but not limited to wheel seals, lube, environmental factors, and the installation process have a much more significant impact on the rolling resistance.”
Newmercman
Had a look at your experts fuel saving measures and I must say he’s trying very hard, I’m sure he must have every type of electronic gadgetry wind deflector and aerodynamic flaps known to man.
After reading about the bloke it’s clear he’s a driver/ driver trainer, he’s doing quite a few miles with a gross weight often less than we put on an eight wheeler this side of the pond.
I’m not so sure he’s actually checked these bearings himself with a dial gauge, I suspect he’s had someone look at it for him, the said technician to justify his cost told your expert what he wants to hear!
Let’s be honest who would buy a brand new truck then pay to have the hubs removed bearings pressed out and a couple of thou machined off a factory precision made part that’s under warranty I.e. bearing spacers?
You’ve then got to press the bearings back in and put the thing back together, all at a cost to save an unmeasurable amount of fuel!
When I’m after advice I like to ask someone who’s actually done the job successfully not seek advice from someone that’s posting information from another post that’s second or third hand.
My workmate wanted to know if you could estimate how many wheel bearings you and your expert had changed and ensured set up correctly over your careers as drivers/test drivers on trucks and trailers?
If you’ve only observed someone else doing it how do you know if they set them up for maximum fuel efficiency/properly anyway?
If you’ve got to worry how much fuel efficiency your wheel bearings are costing it’s time to look for better paying work or another job!
I looked into fuel efficiency in the late seventies early eighties. The various aerodynamic aids work well but the vehicle uses the advantage gained by giving faster acceleration and better hill climbing, the only way to gain full advantage of the wind deflectors is to reduce the power used so as the acceleration and hill climbing are the same as before fitting but that never happens.
Driving as if you have very poor brakes saves fuel as does pumping up the tyres keeping the revs down and choosing your route carefully, anything else is clutching at staws and saves minimal amounts in my opinion.
The new automatics don’t allow for gear skipping like we used to do, start in second on a slight downward incline and then miss one to use gravity to help get you rolling, I used to use second to start off (9 speed fuller) then fourth then into high range, it’s down to the driver in a lot of cases and you can’t teach some drivers that you will accelerate just as fast using lower revs in a higher gear, I recon that if you gave the vehicle a wonderful exhaust note at the most economical revs then fuel efficiency would improve dramatically.
Just my opinion based on saving fuel as an o/d
Moose, you’re taking it to an extreme with this wheel bearing thing, I said make sure they’re adjusted correctly, if they’re non adjustable then that’s the end of the story, if they are adjustable then check them with a breaker bar with the wheel in the air, you know, the old fashioned way.
How often do I check mine? Never. Well I hit all the hubs with an infrared thermometer during a trip, that doesn’t tell me if they’re incorrectly adjusted, but a higher reading on one compared to its opposite number will tell me there’s an issue of some kind, unless it’s a one off.
However, I’m not worried about mpg, I bought one of the most un-aerodynamic lorries ever made with a notoriously uneconomical CAT engine, I pull big lumps of machinery around weighing up to 170,000lbs and I have my speed limiter set at 80mph, an out of adjustment wheel bearing is the least of my worries.
In the days of London Transport the organisation was almost obsessed with its operating costs. In spite of this it still managed to waste enormous sums of money in its daily operations. However in the late 1940s it did set up an experimental department at Chiswick to investigate modifications to vehicles which might be financially beneficial. One of the experiments related to wheel bearings. Traditionally front opposed taper roller bearings are designed to be a close slip fit over the stub axle with a minimum ’ end float’ (clearance or slack) between the two bearings. LT had found that in London service with stops every hundred yards or so, the brakes heated up the hub to such an extent that this clearance disappeared. The result of this was the the inner track of the inner bearing would spin on the stub axle requiring considerable dismantling, with specialist metal spraying and machining techniques needed to reclaim the damaged stub axle. Various experiments were carried out in the 1950s which arrived at the conclusion which was put into practice sucessfully. This made the inner bearing a press fit on the stub axle and increased considerably the running clearance between the two bearings.
Tyre choice makes a big difference. I’ve just changed from Michelin XDA2+ (which are meant to be group D for fuel) on a drive axle to Goodyear Fuelmax, (meant to be group C for fuel).
Driving style hasn’t changed but I’m now using an extra 3 liters every 100km. To me that’s a lot of money over the tyre’s life. 
Ive actually done an old fashioned tank to tank mpg check, the first time, i got a return of 8,24mpg, and the second time was slightly better, at 8.47mpg, so it just goes to show, that you cant trust the the read out on the dash.
jimmy2loads:
Ive actually done an old fashioned tank to tank mpg check, the first time, i got a return of 8,24mpg, and the second time was slightly better, at 8.47mpg, so it just goes to show, that you cant trust the the read out on the dash.
Does it?..how so!
Lost in France:
Tyre choice makes a big difference. I’ve just changed from Michelin XDA2+ (which are meant to be group D for fuel) on a drive axle to Goodyear Fuelmax, (meant to be group C for fuel).Driving style hasn’t changed but I’m now using an extra 3 liters every 100km. To me that’s a lot of money over the tyre’s life.
The difference in mpg with two sets of identical tyres, one worn to the point they need replacing and the other set fresh out of the box is around 6% in favour of the old worn out rubber.
newmercman:
Lost in France:
Tyre choice makes a big difference. I’ve just changed from Michelin XDA2+ (which are meant to be group D for fuel) on a drive axle to Goodyear Fuelmax, (meant to be group C for fuel).Driving style hasn’t changed but I’m now using an extra 3 liters every 100km. To me that’s a lot of money over the tyre’s life.
The difference in mpg with two sets of identical tyres, one worn to the point they need replacing and the other set fresh out of the box is around 6% in favour of the old worn out rubber.
But how much less distance is being covered due to the reducing rolling radius as the tyre wears, the fuel computer doesn’t know the tyres are smaller, as far is it goes the vehicle has gone further for the same amount of fuel 
