For those with the smaller brake booster unit, this DIY can drastically improve brake performance.
BHPian vivekdewanta recently shared this with other enthusiasts:
Hi Team-BHPians,
After nearly 15 years of ownership with my 2011 Maruti Suzuki Alto, I recently faced a serious issue with my braking system. This led me down a path of diagnosis, DIY experimentation, and eventually a successful brake booster upgrade. I’m sharing the complete process here in case it helps others who may be experiencing similar brake performance issues.
Symptoms & Diagnosis:
It started with the brake pedal becoming unusually hard — not impossible to drive, but clearly not safe in panic braking situations. I initially suspected the brake booster, which in the Alto is a small unit (approx. 6.5″ in diameter, 20″ circumference).
Soon after, the pedal also turned a bit spongy, a typical sign of a failing master cylinder.
Checked with:
- Local spare parts shops
- Authorized Maruti service centres
Unfortunately, while master cylinders were available, the small brake booster used in my Alto was no longer available in the new parts market.
A Note on Brake Booster Variants:
This DIY specifically applies to Maruti Alto models that came with the smaller brake booster, mostly found in earlier variants or base trims. Maruti Suzuki likely used the smaller booster as a cost-cutting measure, which unfortunately compromises braking comfort and pedal feel — especially noticeable over long-term use.
If your Alto has the larger booster from factory, you may not need this upgrade. But for those with the smaller unit, this DIY can drastically improve brake performance.
Below is a comparison of the Small and Large brake boosters with master cylinder comparisons with L-type or downward type and V-type. 
Visit to Mechanic – Partial Fix:
My local mechanic replaced the master cylinder with a used one he had and told me the issue was fixed. But I wasn’t satisfied — braking still didn’t feel responsive or confidence-inspiring. That’s when I decided to take matters into my own hands and do a full brake booster upgrade.
DIY Brake Booster Upgrade – Planning Stage:
Inspired by a similar modification I once did on my old Jeep (story for another day!), I decided to:
- Upgrade to a larger brake booster for better brake assist and pedal feel.
- Retain the new Alto-compatible master cylinder.
- Prepare for a future rear disc brake conversion.
Sourcing the Parts:
Brake Booster: After some effort, I sourced a used larger brake booster from a Type 1 Maruti WagonR from a local scrapyard.
I didn’t use the WagonR’s master cylinder because it had a “V-type” pipe outlet layout, incompatible with the Alto’s downward pipe routing.
Master Cylinder: Installed a brand-new master cylinder compatible with the Alto’s brake line layout.
Master cylinder comparisons with L-type and V-type. Ignore the rope as I couldn’t get the best alternative to hold the hose pipe or NRV hose from touching against the reservoir.
Push Rod Adjustment – Critical Step!
The brake booster has an internal push rod that needs to be aligned properly with the master cylinder.
If the push rod isn’t adjusted correctly:
- Too short = long pedal travel (free play)
- Too long = brake drag or sudden brake lock-up
Normally, a special tool is required to adjust the push rod depth. Since this tool wasn’t available, I:
- Created a DIY measuring tool using cardboard.
- Calculated the exact push rod length using basic geometry.
- Matched it to the master cylinder depth.
Below are the actual master cylinder measurement tool and the one that I made with the help of a cardboard. 
Watch the video on how to use the tool properly.
Installation & Results:
After making the necessary adjustments, I installed the WagonR brake booster with the new master cylinder in the Alto. The process wasn’t plug-and-play — the mounting holes needed slight tweaking — but it was manageable.
Important Installation Tip:
Don’t forget to install the O-ring between the master cylinder and brake booster!
Most new master cylinders do not include this O-ring, and it’s often forgotten — even by professional mechanics. If it’s missing, the booster will leak vacuum, resulting in poor brake assist or a hard pedal feel despite all other components working correctly. I made sure to reuse the original O-ring and had no leakage issues.
Immediate Results:
- Brake pedal is now lighter.
- Braking response has improved significantly.
- Much easier on the legs in city traffic.
Currently still testing with old rotors and pads to ensure reliability. Once I’m satisfied, I’ll:
Install new brake rotors + pads:
Begin the rear disc brake conversion, which I’ve already planned out (measurements and parts list are ready)
Below images are after the successful installation of the Larger WagonR Booster and Brand brand-new Master cylinder L-type. Ignore the red ropes, as these are there to hold the NRV hose from rubbing against the reservoir.
For the tip: Testing a Used Brake Booster at the Scrapyard
While sourcing a used brake booster, here’s a simple but effective method to test it before buying:
Start your car’s engine – this creates vacuum in the intake manifold.
Disconnect the vacuum hose from your car’s booster and connect it directly to the booster you’re testing at the scrapyard (make sure the master cylinder is still attached).
Now, manually push the booster’s push rod (the one that connects to the brake pedal) by hand:
- If it’s soft and moves in easily, the booster is good.
- If it’s stiff or requires effort to push, it’s likely bad and not worth buying.
Also, open the master cylinder and check inside the booster — if there’s brake fluid present, that’s a red flag. It indicates a leaking master cylinder, which may have already compromised the booster.
Never reuse an old master cylinder from a scrap unit. Even if it appears fine, they often fail within 3–4 months (speaking from personal experience).
What’s Next?
Rear disc brake conversion is the next step. All calculations and fitment checks are done. Currently sourcing necessary parts.
This brake booster upgrade was the first phase of a broader braking system overhaul — and a big success!
Attached below:
Photos of the WagonR brake booster installed on my Alto
DIY cardboard push rod depth measuring tool
YouTube link showing how to adjust the brake booster push rod
Conclusion:
Maruti may have prioritized cost-cutting with the small booster, but this upgrade brings factory-like braking back to my Alto — maybe even better. I hope this post helps others who are considering a similar upgrade.
Happy to answer questions, share part numbers, or offer fitment tips to anyone attempting this.
Drive safe.
Check out BHPian comments for more insights and information.
