Frp Alcon rebuild stainless steel bolt set

Full set of stainless bolts for rebuild of calipers including 2 with nylocs to replace the pad retaining pin.



£16.50 posted or collection from Coventry or Birmingham

Simon

These are sourced from a local engineering suppliers, not like some of the cheap Chinese rubbish on ebay

calipers are supposed to be fixed together with 12.9 bolts ideally... you can get away with stainless but the difference when you torque them up on the thread strength is very noticable...



Chris

Can you let me know what torque setting the bolts need to be tighten too please?

Fcking tight I do them, lol.

I am in the process of a full overhaul of the suspension & brakes on FMC23. As regards the Alcons I have ordered 12.9 Grade Zinc plated replacement Allen bolts. I would not advise using stainless in this application, they are not up to the job. As regards tightening - use a correctly set torque wrench is the only way. Thread retention for 10.9 & 12.9 - use medium or high strength thread lock.............Found this on the net. It serves as a good insight.................

Grades of Bolts - An Engineer Rambles

Is it possible to write an essay about bolts? If you are a Engineer, and your livelihood depends on machine design, then its possible to write a book about bolts.

There are four grades of bolt in common use. Most bolts which you will come across will only deviate slightly from these three grades. The lowest grade is 4.6, commonly known as commercial grade. Next comes grade 8.8, known as structural grade, then 10.9, and finally, the highest grade is 12.9, known as high tensile bolts. The first number represents the ultimate tensile strength of the bolt, 400 MPa, 800 MPa, 1000 MPa or 1200 MPa respectively. The second number represents the point at which the bolt will permanently stretch. (Officially, the 0.2% proof load stress). A 4.6 bolt permanently stretches at 60% of its ultimate, an 8.8 at 80%, a 10.9 at 90% and a 12.9 at 90 %.
Grade 12.9 bolts Grade 12.9 bolts are most often supplied as socket head bolts or socket head cap screws with hexagon socket (Allen Key) drives. Grade 12.9 bolts can also be obtained with hexagon heads. Popular brands of grade 12.9 bolts are Unbrako and Holo-chrome. It is possible to obtain zinc or chrome plated versions, but not galvanised. Galvanising destroys the heat treatment of the steel.

********* Beware! it is not possible to source 12.9 grade stainless steel bolts. 316 and 304 stainless steel will only be equivalent to grade 4.6. They may look cute in an engine bay, but they do not meet the grade.

*********Grade 12.9 nuts are not made.

Grade 8.8 bolts are usually supplied as hexagon head bolts, often galvanised, sometimes zinc plated, but usually black. They are distinguished by the three radial lines on the head, or these day, by the numerals 8.8 stamped on the head. Grade 8.8 nuts are taller than grade 4.6, but do not have any distinguishing marks

Grade 4.6 bolts come in a vast array of configurations. Hexagon head, countersunk slot drive, galvanised, zinc plated, oxy-sealed (ie gold zinc plating), chrome plated. On a motor vehicle, grade 4.6 bolts are used to hold on trim parts and light objects. Grade If you need to replace a bolt, and the grade is doubtful, use grade 8.8 and be safe. The head of a grade 4.6 bolts is easily scratched with a file, not so a 8.8 bolt.

How do you tighten a bolt?
Grade 12.9 bolts are tightened with a torque wrench, right up to their 90% proof load. There is no other effective way to tighten a grade 12.9 bolt. Automotive manuals will give the tightening torque required. Grade 12.9 bolts do not work effectively with spring washers or shakeproof washers. These don't bite into the hardened surface of the bolt. There are only two ways of adding extra security to grade 12.9 bolts. Use Loctite on the threads or drill the heads and wire the bolts. It is possible to buy pre-drilled cap screws. Mating surfaces of a 12.9 bolted joint are not painted. For serious work, never re-use a fully tensioned 12.9 bolt. For Grade 10.9 do similar.

Grade 8.8 bolts are tightened by the part turn method, torque wrench, or by using load indicating washers. In the part turn method, the bolt is done up to snug tight, and then advanced one, two or three flats of the hexagon, depending on the size, length etc. The torque wrench method is used commonly, often in the form of an air operated rattle gun. Special load indicating washers, such as Coronet washers can be used. These have dimples which indent the mating surface. A feeler gauge is used to determine the pre-load. Grade 8.8 Bolts are used in High Strength Friction Grip applications. If this is the case, the mating surfaces must not be painted or galvanised. For added security of the joint , use any one of the plethora of systems such as spring washers, shakeproof washers, Loctite, wired heads, split pins and castle nuts, locking tabs, lock nut or patented nut systems (Nyloc is common). For serious work, use castle nuts, either with split pins or wired together in groups. Also for serious work, do not re-use fully tensioned grade 8.8 bolts, Nylocs, split pins etc.

Grade 4.6 bolts are not pre-tensioned in the joint. They are tightened to snug tight only. For all intents, this means a reasonable hand effort on a spanner. Use good springy chrome-moly spanners, and never put an extension bar on the spanner. All of the security systems available for 8.8 bolts are available on 4.6 bolts. If you need much more than a spring washer, question whether the joint really requires an 8.8 bolt. Mating surfaces of a grade 4.6 bolted joint are usually painted prior to assembly.

As to torque settings, according to Ford TIS the caliper piston housing bolts :- 58Nm !!! i.e as tight as the caliper mounting bolts, also 58 Nm. On that basis, bearing in mind the article quoted above, those stainless bolts will do one of two things. A. SNAP or B. Not be tight enough. Personally I wouldn't use them.

Further to the above:- 'Tightening torque A2 & A4 M8 x 1.25mm stainless caphead bolts 21Nm' !!! Courtesy of google. Conclusion:- Not fit for purpose in this application