DOT 5 vs 4 - Brake Pedal firmness - Brembo conversion

[klammer76]

Ok, bear with me. I have a 2002 FLHTC. Converted 2 years ago to Brembo brakes front and rear. Brembo MC, and calipers up front. Totally disassembled, cleaned, new seals and installed. Running DOT 5 up front and brakes are great. Lever very firm and is way better than the original stock set up. No issues and like the DOT 5.

On the rear, new, totally cleaned rear Brembo caliper, correct 208 non ABS line and retained the stock Kelsey Hayes MC. Running DOT 5. Bike stops fine but pedal travel is very long and I feel it uses all the travel it has. The key here is it requires the Brembo MC to work correctly as designed (same as the front, will work with the stock MC but to get the full effect the Brembo works better due to different bore). On the rear, the stock Kelsey Hayes is a 11/16" bore. The Brembo rear MC is a 5/8" bore. I am going to convert to the Brembo rear MCvery soon. MC is cleaned and have a new line.

So, after the background here is my question:

I have had no issues at all running DOT 5 in the Brembos and several others have been fine also after TOTAL disassembly and cleaning. Will there be and difference in rear brake pedal travel and firmness if I continue to use DOT 5 with the new brembo MC? IE, does DOT 4 give a firmer feel, performance than DOT 5 or do you think 5 will be the same after switching to the correct MC for the rear caliper?

Thanks for info, input etc.

[nomadmax]

Following this one with interest as I'm about to convert my ABS bike into a non ABS bike after the ABS ECU failed during the dealer recall procedure. I have everything I need except for the seal kit to rebuild the calipers.

[harley_cruiser]

I don't think you are going to see that much difference (with your problem) with the fluid change. How much travel before the brake starts to grab?  Is that what is causing the problem? The larger mc that you have now will push more fluid faster but will give a harder feel than the 5/8. Going smaller will make the distance even longer.
Is the rotor warped?

[N-gin]

DOT 5 is NOT for ABS.
DOT 5 will have LESS firm pedal feel
DOT 5 is silicone based

If it was me I' use DOT 4. 

[rbabos]

DOT 5 is NOT for ABS.
DOT 5 will have LESS firm pedal feel
DOT 5 is silicone based

If it was me I' use DOT 4.

Dot 5.1 is also fine for ABS.
Ron

[N-gin]

DOT 5 is NOT for ABS.
DOT 5 will have LESS firm pedal feel
DOT 5 is silicone based

If it was me I' use DOT 4.

Dot 5.1 is also fine for ABS.
Ron

Is that 5.1 silicone based? I haven't hear too much about it.

added: never mind no it isn't, its poly-gly based like 3,4

[N-gin]

Ok, bear with me. I have a 2002 FLHTC. Converted 2 years ago to Brembo brakes front and rear. Brembo MC, and calipers up front. Totally disassembled, cleaned, new seals and installed. Running DOT 5 up front and brakes are great. Lever very firm and is way better than the original stock set up. No issues and like the DOT 5.

On the rear, new, totally cleaned rear Brembo caliper, correct 208 non ABS line and retained the stock Kelsey Hayes MC. Running DOT 5. Bike stops fine but pedal travel is very long and I feel it uses all the travel it has. The key here is it requires the Brembo MC to work correctly as designed (same as the front, will work with the stock MC but to get the full effect the Brembo works better due to different bore). On the rear, the stock Kelsey Hayes is a 11/16" bore. The Brembo rear MC is a 5/8" bore. I am going to convert to the Brembo rear MCvery soon. MC is cleaned and have a new line.

So, after the background here is my question:

I have had no issues at all running DOT 5 in the Brembos and several others have been fine also after TOTAL disassembly and cleaning. Will there be and difference in rear brake pedal travel and firmness if I continue to use DOT 5 with the new brembo MC? IE, does DOT 4 give a firmer feel, performance than DOT 5 or do you think 5 will be the same after switching to the correct MC for the rear caliper?

Thanks for info, input etc.

you are using 5 or 5.1?
I know what you wrote but just for clarification.

[klammer76]

This is a conversion on a 2002 FLHTC, it is NOT an ABS system. I am using DOT 5 in the Brembo system up front and the lever is rock hard (something I could never get with the original system). The key that I have seen is the brembo calipers need to be matched to the correct MC that goes with them. I did that for the fronts and all is very good. I am now doing that to the rear (this will require some modification to mount it, that is why I didn't do it originally). Non ABS brembo's will work fine with DOT 5. DOT 5 is not to be used in ABS systems.

My question is for anyone that may know, does DOT 4 give a firmer pedal than 5?

I don't think using 4 in the 11/16 bore original MC will give a better pedal. I believe this system needs the 5/8 that it was designed for. I have to check my notes as I measured everything when I had the calipers apart. The Brembo pucks/bores in the caliper are different size than the Kelsey Hayes.

[klammer76]

Following this one with interest as I'm about to convert my ABS bike into a non ABS bike after the ABS ECU failed during the dealer recall procedure. I have everything I need except for the seal kit to rebuild the calipers.

QTM used to sell the seals but don't offer them any more. I assume either HD or Brembo (or both) put a stop to it. They were very pricey @ $49.00 a set. You can split the calipers and use denatured alcohol to clean everything. I also used electrical contact cleaner. I cleaned the seals and used new in two calipers and used the originals in one other. Small smear of NAPA Sil-Glide (not brake fluid) and reassembled. Be very careful not to lose the small o-ring that goes between the two caliper halfs, you won't be able to buy that o-ring. Just be careful removing the seals and reinstalling and you will be fine. PM me if you need seal info.

klammer

[rbabos]

Following this one with interest as I'm about to convert my ABS bike into a non ABS bike after the ABS ECU failed during the dealer recall procedure. I have everything I need except for the seal kit to rebuild the calipers.

QTM used to sell the seals but don't offer them any more. I assume either HD or Brembo (or both) put a stop to it. They were very pricey @ $49.00 a set. You can split the calipers and use denatured alcohol to clean everything. I also used electrical contact cleaner. I cleaned the seals and used new in two calipers and used the originals in one other. Small smear of NAPA Sil-Glide (not brake fluid) and reassembled. Be very careful not to lose the small o-ring that goes between the two caliper halfs, you won't be able to buy that o-ring. Just be careful removing the seals and reinstalling and you will be fine. PM me if you need seal info.

klammer

I just discovered that yesterday about QTM on Brembo seals.No listings.  No problem, ebay has plenty of kits and the seals are actually the same as some Honda's use.
As far as I know, these fit Brembo calipers.
Honda part # 45209-961-006
Honda part # 45109-961-006
Another interesting tidbit. Inverted v rod forks use an o-ring on the tube to axle block should anyone take one apart. Other then me or Traxxion it's not likely to happen since with HD you need to buy the whole slider with axle block.   It's a bastard size 1/2 way in between two mm sizes. Honda is the only available source for these as well and common. There's always a way.
Ron

[klammer76]

Thanks Ron. I was going to advise about ebay in a pm but it's out there anyway. Would love to know if it was HD, Brembo or both that shot QTM down.

As a side note, spoke to a friend where I work on my bike (drag car fab shop). He said the same as was mentioned, 5/8" MC should travel further and be softer, 11/16 sould travel less and have harder pedal feel? I had it backward in my head. That is just in theory with only compairing bores . Might be different things inside the 5/8 MC vs the 11/16? One thing he asked me was are the pedals the same. The 5/8 has a longer pedal than my 2002 had stock (I believe). However, I did change the pedal years ago to an extended Howards Horns pedal. That may be some of my issue with long travel? Can't recall year HD started to offer the longer rear extended style pedal. I di know that all the brembo rear units I have checked have a short travel, hard pedal feel ( with the 5/8 bore Brembo MC with DOT 4 stock).

[rbabos]

Thanks Ron. I was going to advise about ebay in a pm but it's out there anyway. Would love to know if it was HD, Brembo or both that shot QTM down.

As a side note, spoke to a friend where I work on my bike (drag car fab shop). He said the same as was mentioned, 5/8" MC should travel further and be softer, 11/16 sould travel less and have harder pedal feel? I had it backward in my head. That is just in theory with only compairing bores . Might be different things inside the 5/8 MC vs the 11/16? One thing he asked me was are the pedals the same. The 5/8 has a longer pedal than my 2002 had stock (I believe). However, I did change the pedal years ago to an extended Howards Horns pedal. That may be some of my issue with long travel? Can't recall year HD started to offer the longer rear extended style pedal. I di know that all the brembo rear units I have checked have a short travel, hard pedal feel ( with the 5/8 bore Brembo MC with DOT 4 stock).

Don't know but it's BS either way. Greed likely. I recently ran across another deal where you can no longer just change a simple 10$ thermostat in a v rod. There was a time where you could.  You now have to purchase the whole damn t stat housing with thermostat at a bloated price of course. So far no cross match for t stat only as it's an oddball size.
Ron

[Hossamania]

As far as a difference in pedal feel between the two different fluids, I don't think there will be a marked difference. There may be some, but it will be slight and probably not noticeable. Matching the correct mc is more important.
Also, I seem to remember that dot5 has a higher boiling point.

[harley_cruiser]

He said the same as was mentioned, 5/8" MC should travel further and be softer, 11/16 sould travel less and have harder pedal feel? I had it backward in my head. That is just in theory with only compairing bores .

Smart friend, did he tell you to look for a mechanical problem like a warped rotor or bad MC?
Like Hoss added most people are not going to notice the difference between dot 5 and 4, 5.1. unless there is air in the system.
Pump up the brake and see if it gets better, firm, if it does let it sit for a  minute and press the brake again, if it is soft, goes in, then the master is bad. If it stay hard then roll the bike back at least one rotation of the rotor, if the pedal goes soft then you have a warped rotor.

[harley_cruiser]

And did you bleed it real good?

[klammer76]

He said the same as was mentioned, 5/8" MC should travel further and be softer, 11/16 sould travel less and have harder pedal feel? I had it backward in my head. That is just in theory with only compairing bores .

Smart friend, did he tell you to look for a mechanical problem like a warped rotor or bad MC?
Like Hoss added most people are not going to notice the difference between dot 5 and 4, 5.1. unless there is air in the system.
Pump up the brake and see if it gets better, firm, if it does let it sit for a  minute and press the brake again, if it is soft, goes in, then the master is bad. If it stay hard then roll the bike back at least one rotation of the rotor, if the pedal goes soft then you have a warped rotor.

MC was new, rotor and pads new also. Bled fine.

[Maddo Snr]

My question is for anyone that may know, does DOT 4 give a firmer pedal than 5?

Short answer is yes but only slightly.

The problem is that most seal specs are NOT compatible with both Dot4 AND Dot5. If, and only if, you are 100% certain the seals are compatible, the whole show would need a thorough dismantle and clean (being careful to use an inert brake cleaner) before swapping fluid types.

Just for the record, DOT4 seals dislike DOT5 fluid more than vice-versa. The extra boric acid in Dot5 seemingly the culprit. Be warned, the results of stuffing this up are ugly...don't even think about silicon based fluids, they will always feel spongier and wreck seals.

[klammer76]

Ok thanks, I'm good from here. As I stated, calipers, seals etc were all dismantled and cleaned two years ago when I converted. DOT 5 has worked fine, especially in the front system that uses the matched Brembo MC. The rear works fine except I want a firmer pedal which I believe I will get with the proper MC for the Brembo caliper. All I was looking for was if 4 gives better pedal pressure than 5. I'm set from here.

Thanks,
klammer

[Maddo Snr]

Like Hoss added most people are not going to notice the difference between dot 5 and 4, 5.1. unless there is air in the system.

I can pick 4 from 5 on the the front with the change in lever feel and on the rear with the point of lockup. Maybe 30 years of prepping race bikes has made me a little more tuned in but I doubt it.

As for 5.1, that feels like someone has put foam rubber under each brake pad. There's some very good reasons silicon-based fluids have almost disappeared from factory designs, feel is one of them. 

[klammer76]

Going 4 on the rear, staying 5 on the front.

[PoorUB]

Going 4 on the rear, staying 5 on the front.

That would make me crazy. I would put the same type of fluid in both.

[Hossamania]

Going 4 on the rear, staying 5 on the front.

That would make me crazy. I would put the same type of fluid in both.

After I changed fluid the first time two years later, at least one of them would have both types in it!

[klammer76]

Going 4 on the rear, staying 5 on the front.

That would make me crazy. I would put the same type of fluid in both.

Why would it make you crazy? I have owned this bike since 2002 and will be the only owner. I know it inside and out. I'm certainly capable of knowing what I have and where, plus, I keep detailed notes on everything and denote any deviations that have been made in my SM. It's a non issue. The reason to keep the 5 in the front system is, it works fine and is not a danger to the paint should something unexpected happen.

[harley_cruiser]

Going 4 on the rear, staying 5 on the front.

That would work for me let us know how it works.
I'm thinking about doing this on the front of my 01 fatboy, did you use take offs from a late model?

[klammer76]

Going 4 on the rear, staying 5 on the front.

That would work for me let us know how it works.
I'm thinking about doing this on the front of my 01 fatboy, did you use take offs from a late model?

Yes, late model take offs. For the front: Calipers, new braided lines from Magnum Shielding, late model MC (for Brembo). Calipers & MC from ebay. SE floating rotors (warped the stock ones fairly quickly), EBC pads. The front conversion is very straight forward & works very well.