yellow 250 desmo front brake pads

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blethermaskite
Posts: 477
Joined: Thu Mar 01, 2018 1:06 am
Location: northern ireland

yellow 250 desmo front brake pads

Postby blethermaskite » Wed Oct 24, 2018 12:35 pm

Hi all,
Anyone got real life experience on best make and/or grade of brake pads for my 250 desmo disc, I currently have 'new' ferodo road pads installed with about 200 miles of bedding in, stops ok but the brake seems to lack bite ( I am not using the standard master cylinder, but a brand new 12mm bore 600 monster master cylinder).
Cheers,
George

double diamond
Posts: 555
Joined: Thu Apr 28, 2011 1:20 am

Re: yellow 250 desmo front brake pads

Postby double diamond » Thu Oct 25, 2018 4:22 pm

I would say the issue you’re experiencing is not due to pad friction material but, rather, the master cylinder you’ve installed. As I recall, the 250 Desmo has a Brembo F05 caliper. A 12mm master cylinder is too big for the Brembo F05 caliper. You’re not getting enough leverage ratio. There is some direction on this subject at http://www.vintagebrake.com/mastercylinder.htm Personal preference is a big factor in brake feel. I don’t entirely agree with the ratios suggested on this chart, preferring greater ratios, but I’ve spoken with others who have been satisfied with the results. The chart suggests that a Brembo F05 caliper (2x32mm pistons) should have a master cylinder that is actually off the chart to arrive at the ratio suggested (i.e. 27:1). According to the chart, you would want a master cylinder with an 8 or 9 mm bore. What was the bore size of the original master cylinder that you replaced with the 12mm master cylinder?

Matt

blethermaskite
Posts: 477
Joined: Thu Mar 01, 2018 1:06 am
Location: northern ireland

Re: yellow 250 desmo front brake pads

Postby blethermaskite » Thu Oct 25, 2018 6:19 pm

Hi Matt,
Thanks for your reply, It is my understanding (rightly or wrongly ??? ) that all disc brake yellow desmo singles came standard with a twin bleed nipple " halo" logo PO8 brembo L.H. front caliper.......certainly that's what's on mine (and mine is an original spec. uk bike), the original front brake master cylinder which is also brembo is as far as I remember 15mm bore. In the past both of my previous yellow desmo singles which were also disc brake models had dreadfully bad front brakes requiring massive hand pressure to function,........so I did a lot more research on this current bike to try and solve the problem......several brake experts advised me that the reason the standard front brake does'nt work properly is down to the leverage ratio (as you correctly advised), apparently due to the overall standard set up being something of a miss matched parts bin lash up by the factory at the end of single's production.
So......to get the leverage ratio better I was advised to use a 12mm bore master cylinder......and there is no doubt the improvement in brake performance is dramatic in comparison to my previous two desmo disc bikes, I mean I am now using two finger pressure at the lever, my lack of 'bite' is probably a personal preference and that's why I was asking for others experience with pad makes and grades.
Cheers,
George

graeme
Posts: 938
Joined: Sun Mar 25, 2012 12:00 am
Location: Tasmania Australia

Re: yellow 250 desmo front brake pads

Postby graeme » Thu Oct 25, 2018 7:47 pm

Hello George,

08 is the original single caliper as you have said.
I seem to remember the master cylinder being close 16 mm
I had mine sleeved down to 12mm
Much better but still a very wooden feel.
Some years ago I (20 or more) I tried different pads without any improvement
I think that a smaller master cylinder bore would help but at that time I couldn’t find a smaller piston to try.

Good luck
Graeme

double diamond
Posts: 555
Joined: Thu Apr 28, 2011 1:20 am

Re: yellow 250 desmo front brake pads

Postby double diamond » Fri Oct 26, 2018 1:52 pm

My BMW has twin F08 calipers. Came standard with a 15mm master cylinder. I changed that to 13mm and would try a 12mm. A single F08 with 12mm master cylinder is in the ballpark but you could go to a 10 or 11mm.

Ferodo has a number of friction materials available for the F08 caliper. Their website (https://www.ferodoracing.com/products/m ... and-shoes/) has performance charts to compare the various compounds. If you know what friction material you have installed, the charts might offer some guidance. I haven’t noticed much difference with different pads but haven’t tried their full range of materials. As you can see with the high performance materials, you have to get them hot to realize their full potential. SBS, EBC, Vesrah, etc. all offer a choice of friction materials but if you know where you are and what you’re after, you can narrow down the choices. I’d be interested to hear about your results if you do try different pads.

Matt

ranton_rambler
Posts: 439
Joined: Sun Jun 04, 2017 11:33 am
Location: Stafford UK

Re: yellow 250 desmo front brake pads

Postby ranton_rambler » Fri Oct 26, 2018 3:58 pm

This issue of poor brake feel is common on Guzzis. My SP1000 still has linked brakes, so the hand lever operates a single P08 caliper. The standard fit master cylinder is a PS12, which is actually 12.7mm. The Guzzi bible (Guzziology) recommends an 11mm master cylinder to get the ratio right.
I got a brand PS11 with dog-leg lever from Stein Dinse for what seemed a reasonable price (about 100 euro from memory). Their website has Brembo drawings attached to some of the parts so I was able to make myself comfortable that it would fit before parting with the cash.
The brake is absolutely transformed.
Having just looked at Guzziology, it says best choice for a single F05 is 10mm master cylinder. The small-block Guzzis have this brake with a PS12 which sounds like what you have.
I've no idea what pads are in the calipers - whatever it came with when I bought it. Many Guzzi owners in the UK swear by EBC, but I can't really comment.
Ian

blethermaskite
Posts: 477
Joined: Thu Mar 01, 2018 1:06 am
Location: northern ireland

Re: yellow 250 desmo front brake pads

Postby blethermaskite » Fri Oct 26, 2018 4:44 pm

I guess I will just have to try out some different pads and see what results I get re. the feel aspect, I think I'm happy enough with the master cylinder brake caliper set up I have for the moment....( I spent enough money on it for now! ) I was particularly fussy with the caliper which has a full brembo recon kit fitted with teflon coated pistons and stainless hardware, the master cylinder and hose are brand new and the disc is very low miles use and near perfect, .....so......for now its down to pads, I will report back on progress, however winter is setting in here so probably not many more miles of playing left before "putting the baby desmo to bed" till the roads dry again.
For interest, I have also owned a big Guzzi (leman Mk2) with brembo linked 08 calipers which had brembo pads in, and the brakes on that were really wooden too.......maybe we are just spoilt today with super duper 4 pot calipers and radial master cylinders and at I for one am expecting too much from an old design.
Cheers,
George


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