Cowboy C4 brake bleeding
The SunRace brakes on the C4 and Cruiser ST 2023+ - how and why
OnTheRoad2 min reading time
The Cowboy C4 and Cruiser ST from 2023 use SunRace hydraulic brakes. They work well but are slightly less well sealed than brakes on other bikes. After 6 to 12 months they may feel spongy, indicating air in the system or leaking oil. The fix is bleeding with mineral oil.
How do you know it's time?
Three signs:
- The brake lever squeezes further to the steering wheel than before before before it 'takes'
- The braking distance is clearly greater than in the beginning
- The lever feels spongy or resilient - you press and it means it only a meter later
What we do
We connect a hand pump to the brake calipers, push out the old mineral oil and pump fresh oil and bleed fluid through the system. We then operate the levers several times to remove remaining air, check pad clearance and take a short test ride. Allow 30–45 minutes per brake, or 60–90 minutes for both.
What we don't use
On SunRace NEVER brake DOT fluid - that's for other braking systems. Mineral oil from Shimano or similar is what's in it. Sometimes we see this go wrong with other repairers and that can affect the seals.
Frequently asked questions
How often do Cowboy C4 brakes need bleeding?
For a daily-used bike: every 6-12 months. With less use it can be longer.
How much does a bleed cost?
€30.00 per brake on top of the service visit of €45.00 at the door - both brakes together €105,00 total, including fresh mineral oil and VAT.
My brake lever creaks. Does it need bleeding too?
Not necessarily - cracking is usually dirty in the lever mechanism or a loose fixing. We check that on the spot. On C4 there is also a known problem that can break the whole lever at the piston stop; in cracks we replace the lever directly (Shimano MT200 is a popular upgrade).
Ready to book?
Choose an available moment online. You pay after the appointment.