Technical Replacing Multipla Rear Wheel Bearings (Rear Disc Brake Version)

[Jabiru]

Hi There,

My Multi is making a dreadful droning sound over 40mph but it goes quiet when I apply the handbrake. So I reckon it's rear wheel bearings - but has anyone tackled this task on a "rear disc brake" version? Am I going to need any special tools - any ideas on where to get the parts (I'm worried that the kit could be different on the disc brake model).

Any ideas greatly appreciated!
Cheers,
Pete

 

[Zardo]

Hi I have done a rear wheel bearing change twice on a Abarth Punto Evo (without previous experience). It has disc brakes on the rear, too.

The standard torque wrench I use for switching winter and summer tires is too weak for the torque needed for the axle nut. So I had to buy a basic heavy duty ratchet and a big socket. The socket was so big it would not have fit on my torque wrench anyway. I did not buy a heavy duty torque wrench because there was none available in the shop and after checking prices I decided not to go to another shop. I measured the lenght of the wrench and did a calculation how much forced would be needed if I would step on it with my foot, the result was about 82 % of my body weight at the time. So I decided to give it a try and tighten the nut without a special torque wrench, by "feeling" what would be slighly less than my body weight and measuring the distance.

However, I would recommend getting a heavy duty torque wrench for this kind of work - if you have a friend who's doing mechanical work ask him if he can lend you one.

It is necessary to at least know the exact torque to apply to the axle nut when tightening. I believe it was 240 NM in my case but I could be mistaken (anyway, it's not the same car).

For example, if the lenght of the wrench was 1 m, it would mean 240 NM of force or about 177 ft-lb. If the foot presses down at a distance of 40 cm from the center of the axle, the necessary force would be 1/0.4 * 240 NM or 600 NM, which amounts to 61,2 kg, or about 82 % of my body weight at the time.

Please not that the total lenght of the wrench cannot be used for the calculation because the foot needs some space stepping down on it, so I figured that the distance of the applied force corresponds to the middle point of the shoe.

It's also possible to calculate the exact distance where the foot has to be placed on the wrench if full body weight was to be applied.

The calculations assume that the wrench is in a horizontal position when stepping down on it.

Hope this helps.

 

[Jabiru]

Hi I have done a rear wheel bearing change twice on a Abarth Punto Evo (without previous experience). It has disc brakes on the rear, too.

The standard torque wrench I use for switching winter and summer tires is too weak for the torque needed for the axle nut. So I had to buy a basic heavy duty ratchet and a big socket. The socket was so big it would not have fit on my torque wrench anyway. I did not buy a heavy duty torque wrench because there was none available in the shop and after checking prices I decided not to go to another shop. I measured the lenght of the wrench and did a calculation how much forced would be needed if I would step on it with my foot, the result was about 82 % of my body weight at the time. So I decided to give it a try and tighten the nut without a special torque wrench, by "feeling" what would be slighly less than my body weight and measuring the distance.

However, I would recommend getting a heavy duty torque wrench for this kind of work - if you have a friend who's doing mechanical work ask him if he can lend you one.

It is necessary to at least know the exact torque to apply to the axle nut when tightening. I believe it was 240 NM in my case but I could be mistaken (anyway, it's not the same car).

For example, if the lenght of the wrench was 1 m, it would mean 240 NM of force or about 177 ft-lb. If the foot presses down at a distance of 40 cm from the center of the axle, the necessary force would be 1/0.4 * 240 NM or 600 NM, which amounts to 61,2 kg, or about 82 % of my body weight at the time.

Please not that the total lenght of the wrench cannot be used for the calculation because the foot needs some space stepping down on it, so I figured that the distance of the applied force corresponds to the middle point of the shoe.

It's also possible to calculate the exact distance where the foot has to be placed on the wrench if full body weight was to be applied.

The calculations assume that the wrench is in a horizontal position when stepping down on it.

Hope this helps.

Thanks for the advice on the torque settings. I've already changed one of the wheel bearing hubs without any problems - but you're right - the tightening torque on those hub nuts is immense! I used a two foot breaker bar with a four foot tube and when releasing the hub nut, I was really worried that the breaker bar might snap! Anyway, I used a similar level of brutality when tightening again - not very technical but I'm sure it will about right. I think your idea about using body weight versus distance is better though - I'll try that technique on the next one.