Wheel Spacers

[Guest sandy77uk]

I'm sure i was using ET15 on my Zero with no spacers, I'm running 205's at the rear on mine

[fry61]

I'm sure i was using ET15 on my Zero with no spacers, I'm running 205's at the rear on mine

 

Spot the difference -- 2B+ & mudguards are wheel mounted

[Longboarder]

ET 35 wheels changed for ET15 therefore 25mm spacers is only increasing the offset by 5mm

I have the stick firmly by the wrong end no doubt but do I understand you changed from ET 35 to ET15 and added 25mm spacers.

If that was the case positive numbers mean rim inset so to go from 35 to 15 means the inset is reduced by 20mm. To put a 25 mm spacer on then adds a further -25 meaning you end with an effective ET -5, a small outset or negative offset and you have moved the rim a total of 45mm (1.8") away from the car body.

 

Nigel

[fry61]

Looks like I've got the numbers the wrong way round Nigel;do my thoughts come out right if the ET change was the other way round? Wheels & tyres as RH supplied (6.5J ??) fouled bodywork on drivers side;Changed these for "all weather" tyres on 5J rims,then needed 25mm spacers to give clearance for hub mounted rear mudguards.

 

Wheels fitted where Minilite style 14" from a Ford Ka.

[Longboarder]

Removing ET15 and replacing them with ET35 increases inset (or positive offset) of the rim by 20mm (closer to the car).

Generally the hub stays in the same place but a 25 mm spacer effectively moves it and gives 25mm more body clearance.

So you have gone 20 in and 25 out so end up with 5mm extra body clearance.

 

Always think of the rim moving and the wheel centre staying still (cos its bolted to the hub!)

Rim moving towards the car, inset (or positive offset) and is an ET plus number.

Rim moving away from the car, outset or (negative offset) and is a negative number.

The overall term Offset is poor and I think Set would be better.

 

Nigel

 

(I will put pen to paper for the mag on 'wheel offset' which most of us find confusing, as I think I now understand it. Famous last words?)

[fry61]

So I got my figures back to front but my resultant answer was correct;I think? Coupled with narrower rims did this improve/worsen the clearance? Fortunately the wheels have gone round & round for several thousand miles now so hope all is good;it's always useful to have others input so I can keep a close eye on bearings & mounts, your piece for the mag will be welcomed.

[Longboarder]

If you change from 6.5 inch tyres to 5 inches that's 1.5 inch reduction. The tyre centre line of the tyre still sits on the centre line of the rim so you loose 0.75 inches each side. Which is another 0.75inches or 19mm clearance on each side of the tyre.

 

Nigel

[maccavvy]

Quick update.

got some bolt on spacers from a member on locost...for a tenner..bargain

[speedtripledan]

My 2b had et 15 i took these wheels off and the new owner put the same wheels on but et 35. the wheels went inward and would not fit with out 20mm spacers....

[Longboarder]

Don't think of the 'wheel' moving. Think/imagine the wheel on the car. The wheel centre/mounting face is bolted to the hub. Neither move in or out! It's the rim that moves relative to the mounting face which if stationary/fixed! If you start from ET 0 the rim can move inwards towards the car called inset, also called positive offset because the ET number is plus something. Only think of the rim moving relative to the wheel centre/mounting face. With the wheel on the car that's not hard to understand. The rim is inset.

Starting again from ET 0 the rim can also move outwards relative to the mounting face, away from the car, called outset, also called negative offset because the ET number is now negative. The rim is outset.

 

( I have imagined a magical variable offset wheel which does not exist. In real life to play like this you need a pile of wheels with various ETs. ET 0 when the mounting face and rim centre line are in the same plane, some inset wheels ET15 and ET35 and some outset wheels ET -15 and ET-35. I dislike the term offset. Should be Set. The off bit sounds descriptive suggesting a movement in an offwards direction but it's the overall subject name. )

 

One of the reasons this subject is confusing is we often look at the wheel off the car. We see a big blob of tyre and rim and the position of the wheel centre is not clear and its only a small bit in the middle. So your mind gives the rim/tyre prominence as the big bit and you naturally think of the wheel centre being in different positions inside the big bit and inset/outset stops making sense as does the maths.

 

Going back to notimpressed's car above with wheels ET 15 i.e. the whole of the rim, that's outside edge, centreline, inside edge and tyre is positioned 15mm inwards on the wheel centre compared to an ET 0 wheel. If you take the wheel off the car you could measure from the centre line of the rim to the mounting face of the wheel centre and they would be 15mm apart.The new owner puts wheels with ET 35 (rim inset 35mm) on the car. Remember the wheel centre stays put, bolted to the hub. The rim is now inset 35mm (from the mounting face/hub) which is pretty obviously 20 mm closer to the car than a wheel with ET 15. Makes sense? I think so. So with the rim 20mm closer to the car he started getting rubbing problems on the tub or shocker. So he had to put on wheel spacers of 20mm (a spacer can only change 'offset' by a minus number) and eureka, rim, tyre and wheel centre move 20mm away from the car and he's back to where he started with effective ET 15. ( ET +35, spacer -20 = +15)(inset)

Say the new owner got a great deal at Halfords, four rims ET -15 with tyres. £250. Bargain? Probably not. The rim would be15 mm outset from the mounting face. The rim would be going from notimpresseds ET 15 which worked fine to ET -15. The change is 15mm in from the zero position to 15 out from the zero position, total of 30mm outwards and the tyre would probably rub on the arch. And a spacer would not help as it is extra outset so minus mm and would make things worse.

 

It is all logical if you just think of the wheel on the car, mounting face bolted to the hub and the rim able to be inset or outset from a fixed position of the wheel mounting face.

 

Nigel

[speedtripledan]

Just put my comment as a practical example of what happens, same has happened on the westy the et 15 wheels needed 5mm spacers as the orig wheels were et7

 

Dan

[Longboarder]

Absolutely perfect example and I seized the chance to pound the message home. Don't feel pounded personally. I get these hobby horses that I ride round on like a certain brand of fuel pump pre-filter being the spawn of the devil. Besides the children don't listen to me any more. 'Dad, I'm thirty. I got the message. Don't go on and on! ' So unreasonable, so I have to bend some else's collective ears.

If I can prevent just one breakdown on the M4 on a wet Friday night in October then I have saved Hoodieism entire.

 

Nigel

[speedtripledan]

Keep going on some of your electrical drawings have helped me no end!