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SRAM chainring 48/35 torque settings
#1
Hey, I lost a bolt on my SRAM chainring 48/35 and noticed that the rest were loose. What are the torque settings for this?
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#2
Most people will recommend about 6~8nm for chainring bolts. I tend to do about 7-ish.
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#3
@Bibacious you should contact the manufacturer and get their specification. Since I do not know what it is for SRAM equipment, I will not tell you. Manufacturers do not all use the same specs or tolerances; and yet many do. Skip to the end of this post if you desire for a quick "answer"; or read through it and partake of my knowledge and experience.

I have never used a torque wrench on any bicycle repair or build. I have never had bolts loosen up or had one break on me after building and repairing bikes for over 3 decades. I have had one bottom bracket bracket cup loosen during that time (thankfully on my personal bike), but such is the design of old Italian and French BB's that due to thread direction precession can occur (that is the reason why left side pedals have lefthand threading).
Regardless of what the torque spec is you should (and often manufacturers build bikes using it) use a thread locking compound (I use medium grade) to keep bolts from inadvertently loosening even if you did not properly torque the fastener. When doing engineering and automotive I do use a torque wrench (as well as many of pieces of messuring equipment), but those wrenches are routinely (every year for non-certified work; within 6 months for certified work) tested through their designed range of use and calibrated by a NIST certified business. Using a torque wrench does not guarantee anything, and it certainly does not mean very much if its calibration is not correct in the first place. All decent torque wrenches should come certified from the factory that they are properly calibrated, but that is only good for the first year (same as if you got one calibrated), upon being purchased. Go into a bike shop and ask them to show you their torque wrenches; there should be a NIST certifcation label on it; ask them to see their pressure gauges. They are supoosed to be professionals and can certainly afford to keep, and should keep, their equipment in good working condition to include verifying and calibrating their equipment. The more any measuring device is used (like a torque wrench or pressure gauge at a bike repair/assembly shop), the more it may potentially get out of calibration (usage does mean it will be out of tolerance, but you cannot verify that on your own except as discussed later*). Cheaper wrenches may not even be calibrated properly or at all when purchased so there is just as good of a chance that you might over or under tighten a fastener/component even if you use the wrench and adjust your work to the manufacturer's specs. Having experience doing this kind of work goes a long way into doing it correctly even without using tools like torque wrenches. Bikes were not falling apart 40 to 50 years ago and earlier when there were no torque specs provided because experienced people were buiding and repairing bikes, cars, etc. Most problems occur due to inexperience, and I guess that is why manufacturers now put out specs on everything because they need to avoid legal liability should things fail due to improper assembly in our ever increasingly litigious world. *There is a way to use uncalibrated equipment (usually already having been calibrated, but with the certification having expired) which involves a "field calibration". That is done by comparing the function of an uncalibrated/expired calibration piece of equipment to a known certified calibrated (within its time period of certification) piece of equipment when you might have multiple pieces of the same equipment and need to ensure that something is still accurate prior to and/or after heavy use or potential damage (e.g. equipment is dropped). The certified equipment is to verify this is NEVER ACTUALLY USED to perform the tasks of the equipment you are "field calibrating" except as a means to check your regular euipment. This is meant to ensure that it is not itself getting out of calibration during its time period of certification. We did this regularly at my shop, but it is usually not feasible on a small scale since now you have the keep an essentially pristine set of gauges, tools, equipment in a certified condition that are generally not ever used. The side benefit is that if you find a bad piece of epuipment you can immediately use that "new" equipment and then replace it with new euipment as your next piece for future "field calibrations". This also provides you with a whole set of certified equipment for when the regular use equipment is sent off for recalibration.

Sorry to go into this in such detail, but I am sick of numbers (unless verified as actual manufacturer's specs are referenced; such as those often found in their manuals or on the equipment itself) being given in a casual manner even with the best and most sincere intent. It is your bike and your safety, so you can do what you want. But if you are giving information to someone else, or repairing/building something for someone else then it is incumbent upon you to provide information that can be referenced (and generally provide that reference; i.e. via a quote from a manual or link to the info) for determining its accuracy. It is also incumbent upon the recipient to check information given without proper references in order to verify the advice given.
The previous torque specs given might very well be spot on and conform to the manufacturer's own specs, but that is for you to decide. Just as it is your own decision to use measuring equipment that may or may not be accurate.

Here is one example of where I fell (almost literally) prey to a shop that was using a pressure gauge that was out of spec. I was starting a 50 mile ride and had just put on new tires purchased a couple days prior. I mounted and hand pumped the tires to enough pressure to safely ride them, but I wanted to run them at near their maximum pressure (160 psi rated max., ride them at 145 psi due to inevitable increase of pressure due to heat build up from friction, pavement temperature, and sun exposure) and I did not have my "field calibrated" gauge available. I rode a couple miles to the same shop I purchased them at and requested that they be inflated to my specification. I asked (but did not visually verify) if their pressure gauge was accurate (which implies that it is calibrated to within tolerances throughout its range of function, and certification is not expired). I was told yes. Long story short my tire blew out (first and only time that has happened, and the only time I let a shop inflate high pressure tires for me). It takes substantially more pressure to blow a tire since manufacturers rate their maximum pressures well below the blow out and/or rim blow off pressure just to account for inaccuracies of pumps and compressors with gauges, hand pressure gauges, etc. which might not be within a reasonably accurate tolerance. I already assume that most gauges are about within +/- 10% of their given readings so I never pump up my tires to their maximum, and always pump them up at 5 psi over their minimum pressure ratings. Because I actually have calibrated gauges I was able to return to that shop (who admitted that they do not get requests to pump up tires to that high of a pressure as I asked), and used my guage to "field calibrate" their gauge. What was discovered was crazy since their gauge was already over 10% under reading at low pressures and got progressively worse the more the pressure was increased. They were setting their compressor cut-off based on a highly inaccurate gauge (which looked 50 years old, though age would not have mattered if still able to be properly calibrated). Although this may have been a rare case, it goes to show the importance of having the proper equipment maintained in the proper manner, especially when you are using it professionally; and the same thing goes for providing information to others in a casual manner (such as on a cycling forum site) where what you say might be be taken as "gospel truth" without the end recipient of said information having ever actually checked it for accuracy. How would someone feel if I told them to adjust something to a certain spec (whether with calibrated equipment or not) and that piece broke while installing, or loosened up or broke upon usage causing damage to their bike and/or injury to themselves. What legal recourse would they have against me for taking my advice.
There are certainly many times that I provide advice, but it cones fron a point of prolonged and professional experience, yet I provide (I hope) a caveat/disclaimer that one needs to check with their local professional and/or reference actual documentation relative to the topic at hand. There is certainly a lot of advice that can be given casually and where semi-responsible individual can take it to heart or with a "grain of salt", but many times (certainly where defined specifications are involved) both the provider of the advice AND the recipient of same must do due diligence (giver: provide references; recipient: research and verify) to ensure it is accurate.
TRUST BUT VERIFY!
Because I use many "short-cuts and tricks" that are of my own doing and were gained from decades of experience I do not provide them to the general public because they are not verifiable except as anecdotal information coming from myself. I have no problem putting my own property and safety at risk; but I cannot and will not do it wilk the general public (unless you want to provide to me a legal document waiving myself of all liability should things go awry).
Everything I stated earlier to standard professional practice, but whether it is being done or not is another subject for discussion. This why you occassionally hear about doors blowing out of aircraft, structural collaspes of new buildings and bridges, space craft failing, etc., etc. One procedural misstep or short-cut (e.g. using a presumed calibrated piece of equipment) can result in catastrophic failure and potential death). I have never had the liberty of ignoring procedures in my engineering, medical, or business endeavours; but I routinely saw it happen and continue to see it happen (and I have paid personally and professionally by exposing it). Sometimes no adverse outcomes, and sometimes the result is quite tragic.

Okay, off my soapbox to go for a ride on my custom tweaked no front brake bike.



Bibacious,
Just for fun here is what a quick search provided:

Steel SRAM bolts: Torque to 10–12 Nm
SRAM direct mount chainring bolts: Torque to 8–9 Nm or 71–80 in-lbs
SRAM 8-bolt direct mount chainring bolts: Torque to 4 Nm with a T-20 tool

There was no specific link to the previous data I provided, but here is my search entry and the info I copied from the initial google search was the "top of the page" result with, of course, many more results to follow it:
SRAM chainring bolt torque specification

Disclaimer: I did not verify the source as being from SRAM so take it as you will, but this data alone shows that one spec (or range) does not fit all applications (as I already knew from experience; go figure).
That is why I recommend contacting the manufacturer regarding your query. As is well known by myself; in order to provide accurate advice one must be provided with accurate information including any variables which may affect any advice given (i.e. steel, or aluminium bolts!).
Safe riding,
Jesper
Take care,
Jesper

"I am become Death, the destroyer of bicycles." NJS
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