New Nuts and Bolts

sparkypenguin · Post by **sparkypenguin** » Thu May 19, 2022 12:23 pm

Hi all,

Just wondering what the opinion is of using new non model specific nuts and bolts when working on your cars.
In many of the "how to" video's it's suggested to replace them with the same size from local hardware stores etc but surely this does not take into account the strength of the items.

Zedebee · Post by **Zedebee** » Thu May 19, 2022 2:36 pm

Some and some. For safety critical applications such as brakes and suspension, and single use items, I would always go OEM; but for general “fixings”, if you get the same specification from elsewhere you should be OK.

horseless_carriage · Post by **horseless_carriage** » Fri May 20, 2022 2:56 am

Generally I only go for OEM fasteners, I find most of the generic hardware store nuts and bolts have inferior corrosion resistance. A lot of the BMW hardware appears to be hot dip galvanized, whereas most of the hardware store bolts are just black oxide or zinc plated. Also I find sometimes the OEM hardware has special features that are hard to find in the generic hardware section (shoulders, flanges, thread locker, etc). This is at least true for most major car manufacturers, some of the exotic and low production run car manufacturers don’t use high quality hardware.

sparkypenguin · Post by **sparkypenguin** » Fri May 20, 2022 11:30 am

Thanks for replies.
I'll stick to OEM just to be safe!

kis · Post by **kis** » Fri May 20, 2022 11:34 am

Might as well change some to titanium if you're okay paying dealer prices? Worth looking into at the very least

Ewazix · Post by **Ewazix** » Fri May 20, 2022 12:39 pm

I think you kind of answered your own question TBH, fixings are not all created equal! As mentioned, single use items are very specific in terms of tensile 'stretch' and should definitely be replaced with OEM every time, also with anything vaguely safety related or mechanically critical.

Unless you have specialist advice confirming the compatibility of mechanical properties swapping anything from OEM to different materials like stainless or titanium should be done cautiously. It's worth noting that some fixings are designed to be 'sacrificial' i.e. designed to break before a major component, particularly in some engine, suspension or safety structure applications, so 'stronger' is not always better.

sparkypenguin · Post by **sparkypenguin** » Sat May 21, 2022 3:01 pm

@Ewazix - Thanks.

I did not even consider the "sacrificial" angle and obviously very important.
In the past on my van etc I've just tended to reuse whatever bolt comes off so how I would know which are classed as single use items?

SonnyA85 · Post by **SonnyA85** » Sat May 21, 2022 8:06 pm

As long as it's a reputable make it's fine.

Stay away from eBay and buy off autodoc and you will be fine.

Doesn't need to be OEM so long as it's a decent manufacturer. I just bought febi bilstein new wheel bolts for example for mine

kis · Post by **kis** » Sat May 21, 2022 11:13 pm

Single use bolts are often referred to a TTY (torque to yield). There are very few bolts/nuts which fall under this category IMO. Think you can browse the information on the TIS system (Technical Information System) but they closed down the site I used to use.

sparkypenguin · Post by **sparkypenguin** » Fri May 27, 2022 5:47 pm

Job done and MOT passed.
I went with dealer nuts n bolts n brackets in the end as they were the cheapest anyway and I could pick up locally which helped.
I replaced both the rear drop links and I replaced the arb bushes with poly ones.
Getting the arb brackets tightened back up was not the easiest so would suggest getting longer bolts in the future for this job.

Now I've got to figure out why my back end is so low. I thought the new drop links might improve the situation but if anything it's sitting lower than ever. It's got 265? 19's with low profile and I can't even get my fingers between the tyre and rim on the driver side. Hence on fast cornering I can here and feel the tyre rubbing. New springs required or just because my tyres / wheels are too big?

DMike · Post by **DMike** » Fri May 27, 2022 6:05 pm

sparkypenguin wrote: ↑Fri May 27, 2022 5:47 pm Now I've got to figure out why my back end is so low. I thought the new drop links might improve the situation but if anything it's sitting lower than ever. It's got 265? 19's with low profile and I can't even get my fingers between the tyre and rim on the driver side. Hence on fast cornering I can here and feel the tyre rubbing. New springs required or just because my tyres / wheels are too big?

Broken rear springs are quite common in these cars and would be easy to inspect. Which tyre size do you have? 265 width is not standard.

sparkypenguin · Post by **sparkypenguin** » Sun May 29, 2022 11:09 am

Springs are OK.
Tyres are 265 / 35 / 19's

mr wilks · Post by **mr wilks** » Sun May 29, 2022 11:19 am

sparkypenguin wrote: ↑Fri May 27, 2022 5:47 pm Job done and MOT passed.
I went with dealer nuts n bolts n brackets in the end as they were the cheapest anyway and I could pick up locally which helped.
I replaced both the rear drop links and I replaced the arb bushes with poly ones.
Getting the arb brackets tightened back up was not the easiest so would suggest getting longer bolts in the future for this job.

Now I've got to figure out why my back end is so low. I thought the new drop links might improve the situation but if anything it's sitting lower than ever. It's got 265? 19's with low profile and I can't even get my fingers between the tyre and rim on the driver side. Hence on fast cornering I can here and feel the tyre rubbing. New springs required or just because my tyres / wheels are too big?

265 35 19 on a rep CSL would be considered "overtyred" for a 9.5j on a Z4 Si .
255-35-19 0r 265 30 19 being the most widely used .
Have you checked the Et number on the rims ? If you are getting rubbing on the rear the offset could be too low as a stock Si even with 265 35 shouldn't rub on the rear with the right wheel fitment .
Any pics ?

sparkypenguin · Post by **sparkypenguin** » Sun May 29, 2022 12:21 pm

mr wilks wrote: ↑Sun May 29, 2022 11:19 am 265 35 19 on a rep CSL would be considered "overtyred" for a 9.5j on a Z4 Si .
255-35-19 0r 265 30 19 being the most widely used .
Have you checked the Et number on the rims ? If you are getting rubbing on the rear the offset could be too low as a stock Si even with 265 35 shouldn't rub on the rear with the right wheel fitment .
Any pics ?

The only numbers on my wheels are as per photo.
Unfortunately I cannot get the wheel off at the moment to look on the back as my garage door has decided to stop working but I do think you may be correct that the tyres are too big.

: 20220529_120450.jpg (71.84 KiB) Viewed 361 times

mr wilks · Post by **mr wilks** » Sun May 29, 2022 5:35 pm

There is your " problem "

a 9.5j et 27 on rear of a Si is on the borderline of what will fit ( for me its over

) & coupled with a 265 35 profile tyre is making a bad fit even worse .
Ideally you would want 9.5j et 38-et42 with aftermarket wheels , then you could fit a 265 35 & get away with it or better still 255 35 or 265 30 .
The wheels you have are ZM fitment so always popular if you decide they have to go .

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