Braking bad?

[majcd213]

Yep tried Lotusbits, they do have them used I think at around 5 quid each... which is fine but they have a std carriage charge of 10 quid plus vat on that lot makes 17 quid for one used bolt! Im hoping to avoid that unless forced as a last resort!

[Pete Boole]

You could use cap-head bolts - they are strong enough.

Pete

[Jason.goad]

Have a look online for a nut and bolt supplier. They will be cheaper than sj/ lotusbits. On the head of a bolt will be a number. That tells you the strength. The parts manual will tell you the M number ( metric thread) and length.
The best way to remove the caliper carrier and get some heat on it. I am correct in thinking it's a bolt holding the carrier to the upright and not a slider bolt.
It takes quite a lot of force to brake either, so I'd be checking nothing is sticking somewhere.

[majcd213]

Yes. Ive found quite a lot of bolts are sold for motorcycle brake calipers. The lotus bolt is M10 1.25 and 25mm. The odd thing about it is that its only threaded over 12.5mm whereas most 25mm bolts are threaded all the way. The bike caliper bolts do have a small unthreaded shoulder and should certainly be tough enough.lotus bolts were marked 3f88 but I dont know what that means.

[RED BARON]

Hi.
If I was you I would buy new bolts from SJ on such a safety part as a brake caliper at £1.99 each +vat I would replace them all.
I say this as a retired engineer that designed pneumatic tools for 30 years that included air torque units and the manual said that they
have to be torqued up to 65lbf.ft (off hand don't know it in Nm ) which is quite high.

The numbers on the top are manufacture and the 8.8 is the tensile strength and the yield strength.

So to save you hunting for a replacement NEW bolt that you would have to buy and not be sure of the correct strength. Why be unsure
when the right thing is available at SJ.

I am only trying to help you and don't want you to feel I am hounding you but safety first.

Regards.
Ian.

[DavidOliver]

For the bolt to shear off I suspect it was slightly loose and the impact caused by sudden braking caused the shear, and the second bolt might also be loosish. For a graunching sound it is also likely the top bolt failed and the caliper was dragged onto the disc. If it was the lower bolt the caliper would have moved outwards against your wheel. Check disc circumference for scratches or worse still alloy scraping from the wheel.
The replacement bolt must have the plain shank, otherwise premature shearing can occur.
For brakes I never go shy, but in this case and to reduce the 5 quid x 8, you may consider just the front four bolts, the delivery cost/bolt is then not such a burden as a single bolt. Rear brakes take a lot less load.
I suggest you also check the thread of the vertical post and the caliper carrier for twisting.
The torque figure for the caliper bolt is a hefty 50-60 lbs.ft and loctite thread goo is a must.

Dave the cog.

[majcd213]

Hi all. Thanks I agree with all of that. However I tried sjs first of all... Before posting anything here and its the fact that they don't have them that prompted this post. Its not the cost of the bolt that fazes me, just the 10 quid carriage on a single bolt.
I know a fully threaded bolt wont do so it has to be plain shanked at least over some of its lenth. The titanium bike caliper bolts are stronger but have a shank app half the length and I think would be fine. However I've found PNM do still have Lotus original bolts plus their own slightly cheaper substitute, so I can hopefully replace all 4 front as well as all 4 rear as the failure of one means I dont trust the others. The graunching nouse was caused by caliper movement putting the pads over the rusty rim. However my interpretation was well adrift, as braking can't stretch the bolts! Any expansion forces acting across the caliper are fully contained within the torque bracket and the bolts in question arent stressed by this action. This can't therefore be the explanation of my original problem but it is odvioysly something that needs sorting. I'll strip down the rear anyway to remove the bolt stump so Ill inspect the caliper to see if its stuck or blocked. Itll have to wait a week but Ill let you know how I get on.

[AndyC]

Definately worth checking with a local Toyota dealership, they will likely be from there. If they are what I think, then they are Metric fine, which is far less common than standard, and is more common to brakes. Some bolt suppliers will have them.
I'm sure I have some somewhere but the garage is full at the moment as I'm changing sheds over, so just don't know where they are.

[bash]

On a similar subject, Ive just done the rear brakes on a full referb mission including braided hoses seeing as the old ones were 32 years old. After having all the pistons out and checking / cleaning all the bores etc there is a marked improvement in feel. One thing I noticed, when I had the back of the car really high in the air is it was difficult to bleed, in that little fluid was getting through, I presume that this was the G valve doing its stuff cos when I leveled the car it bled up straight away. My one man bleeder that I made consists of a tube with a bolt in the end and a small slit near the bolt and me pressing the pedal, old school but it works. The brakes are never going to feel like an overservoed modern car but they work ok.

Bash

[don.hasi]

Just a thought - would the bolts also be from Toyota?

Unfortunately not. They are as well not available anymore.

[bash]

How are you getting on with this ? Had a couple of thoughts, if your pedal is very spongey , and you've still got the rubber type of flexies on, you could clamp all the flexies, if the pedal is harder its a caliper problem if its still soft you still have some air in the lines. Some improvement can be made to the brake pedal travel though by adjusting the rod between the brake pedal and the servo and take out some of the free travel ( not all of it as you could have a slight binding issue ). You will need to assume the lotus position, upside down head in the footwell, and loosen the 13 mm nut on the clevis first. I found that the best tool for the job was to cut an 8mm open ended spanner down to about 50mm long, put a piece of insulation tape in the jaws of the spanner to stop it slipping off, and you will find that the rod into the servo has two flat faces that will fit the 8mm spanner and adjust out the free play. The reason that it has to be cut down is that there isnt alot of room up there for a full spanner. Make sure the locknut for the clevis is tight when you have finished.
Sometimes the clearance between the master cylinder and the output rod of the servo can be excessive, and I see you've had a new master cylinder. The clearance between the two should be very small, but is hard to measure. On the standard master cylinder the output rod of the servo should be level with the end of the servo, therefore the distance to the end of the master cylinder piston should be level with the mounting face of the cylinder giving a very small clearance. If theres too much clearance there will be too much pedal travel, if there too little the brakes will bind.
Hope this helps.

Bash

[majcd213]

Thanks Bash, I did wonder if I have an adjustment problem as well. I have to sort iut my broken bolt and will check the relevant caliper again before rebleeding and trying again. I want to bypass the G valve as well in case its to blame and Ill add the rod adjustment to the list. I did measure the recess of the piston head from the flange in both mastercylinders and it was less than 1mm difference which I think is negligable... however, although Ive never adjusted the servo output rod (there are many warnings about that), this doesnt mean its never been altered... Adding rod adjustment to the list!

[bash]

Dont delete the G valve, its there to stop the rear brakes locking under heavy braking, if you take it off it will be like putting the handbrake on under emergency braking and you are likely to lose control. The adjustment on the servo / master cylinder doesnt need you to disconnect anything hydraulic, just loosen the two nuts on the master and pull it away from the servo to access the adjuster in the servo.
the g valve is quite a simple device really and is usually a ball bearing on a slope that varies the hydraulic line pressure input to the rear brakes, there are other ways of doing this but apart from sometimes holding a little air giving bleeding issues they dont really go wrong.

Incidentally, if you did delete it and had an accident you would get knocked off by the boys in blue ( black / dirty high vis, howitzer resistant jacket, batbelt..... bobbies arnt smart looking anymore ) ( I know that there is a differnce to looking smart and being smart... I should know )

Bash

[majcd213]

I wasnt going to remove it, just see if I get a firm pedal without it!

[bash]

Sorry, Im not as bright as I look either ( cue comment from Angus... )

Bash