53mpg before tyre change,48mpg afterwards

[bassman]

I check my consumption and mileage brim to brim every week, so, providing my mileometer is correct, I know my mpg, and drive to keep it in the 50 to 55 range. I also reset my computer at every fill up to make sure my mpg is maintained evey week, and if something happens I can spot the error immediately.....I know there are arguments against this "resetting"....but it works for me, so I'm not interested in the "wrongs and rights" of this...

I drove into my pals garage the other day and got 2 remoulds/retreads on the front of my 75....Ive used remoulds for 45 years, without any bother, so I'm again not interested in the "wrongs or rights" of remoulds....When I drove in my OBD was showing its usual 53.7mpg......after getting the tyres fitted, and running 20miles, my OBD had dropped to 50mpg, and then later in the week, continued to drop and seemed to set itself around 48mpg.

Ive not yet filled up this week, so havent done a brim to brim to verify this, but my question is.....Do the members think that this 5mpg drop can entirely be due to the fitting of new tyres to the front.

The remoulds are KingPin Valour rated as 91H......

When I get the chance I will swap the tyres from back to front....and see if that improves the situation

[T-Cut]

If anything, new tyres should improve the figure slightly since they have a larger circumference than worn tyres of the same specification. IMO it's the OBD aggregating.

TC

[MangoMan]

Different tyres/rubber have different rolling resistance - quite normal unless you changed like for like...?

See here: http://www.youtube.com/watch?v=40TpAB818_8

[bassman]

Originally Posted by MangoMan

Different tyres/rubber have different rolling resistance - quite normal unless you changed like for like...?

See here: http://www.youtube.com/watch?v=40TpAB818_8

I'm not that technically minded to be able to understand whether the "rolling resistance" can be converted to mpg, but will take your word for it..

The tyres wernt changed "like for like", but Ive always used remoulds, and often Kingpin, so will at some earlier time(in the 50k Ive driven the car), had new Kingpin remoulds on the front...........without such an MPG drop.

[Billy1mate]

It'll be that heavy air they used.

[DMGRS]

Cold weather - I've lost about 5MPG over the last month or so.

Cold air = dense = more fuel. Also cold engine on choke for longer = more fuel.

[bassman]

Originally Posted by mattyprice4004

Cold weather - I've lost about 5MPG over the last month or so.

Cold air = dense = more fuel. Also cold engine on choke for longer = more fuel.

Yes, I did consider this, but its been 15 to 18 degrees here this week.......... it was only 12 degrees last week and it didnt drop...and I reset the OBD every week.

[myrover2013]

get yourself a set of avon zv5 they are made of 85% rubber and British made at that

best tyres out there for our cars,

[bassman]

Originally Posted by bassman

Did a brim to brim today, and the results agree with the OBD......47.6mpg, which is by far the lowest I've had since running with a duff MAF.

Ive put the new remoulds on the back, and the worn in rears on the front, to see if that improves the mpg.

Done 200 miles since changing the tryres round...its gone up slightly, but only by around 1mpg.......which is not what I was hoping for.....

[Trevor1975]

Originally Posted by bassman

Done 200 miles since changing the tryres round...its gone up slightly, but only by around 1mpg.......which is not what I was hoping for.....

To be honest, going up and down a few MPG is normal, even if you are driving very consistantly.

All it takes is for the wind to pick up, slightly lower pressure in the tyres, a bit of brake bind...

if you are driving to achieve economy like that, ie very gently and not too fast, the smallest things could have a noticeable impact.

I'd say check tyre pressure and tracking. If OK then still dont panic!

48 mpg is still very good for this size of car

ATB

Trev.